Paediatric formulations of second-line anti-tuberculosis medications: challenges and considerations.

There is a growing number of children worldwide accessing second-line anti-tuberculosis drugs for multidrug-resistant tuberculosis (TB); however, there are very few child-friendly formulations. For paediatric use, dispersible tablets offer distinct advantages over liquid formulations and other approaches. This is particularly relevant for TB, where stability, long shelf-life and reduced manufacturing, transport and storage costs are all critical to ensuring that drugs are accessible and affordable. In addition, fixed-dose combinations that reduce the pill burden and provide adequate taste masking may promote long-term adherence to anti-tuberculosis treatment and prevention regimens likely to last many months in children. Partial adherence may result in treatment failure and the further selection and spread of resistant mycobacteria. Unfortunately, no second-line TB paediatric drugs exist in dispersible formulations. We discuss here the main obstacles to developing such tablets and present strategies for overcoming them. We also advocate for timely anticipation of paediatric use when new TB drugs are being developed, and for the development of child-friendly anti-tuberculosis formulations in general.

Isolation and Characterization of Nodule-Associated Exiguobacterium sp. from the Root Nodules of Fenugreek (Trigonella foenum-graecum) and Their Possible Role in Plant Growth Promotion.

One of the ways to increase the competitive survivability of rhizobial biofertilizers and thus achieve better plant growth under such conditions is by modifying the rhizospheric environment or community by addition of nonrhizobial nodule-associated bacteria (NAB) that cause better nodulation and plant growth when coinoculated with rhizobia. A study was performed to investigate the most commonly associated nodule-associated bacteria and the rhizospheric microorganisms associated with the Fenugreek (Trigonella foenum-graecum) plant. Isolation of nonrhizobial isolates from root nodules of Fenugreek was carried out along with the rhizospheric isolates. About 64.7% isolates obtained from Fenugreek nodules were gram-negative coccobacilli, 29.41% were gram-positive bacilli, and all rhizospheric isolates except one were gram-positive bacilli. All the isolates were characterized for their plant growth promoting (PGP) activities. Two of the NAB isolates M2N2c and B1N2b (Exiguobacterium sp.) showed maximum positive PGP features. Those NAB isolates when coinoculated with rhizobial strain-S. meliloti, showed plant growth promotion with respect to increase in plant's root and shoot length, chlorophyll content, nodulation efficiency, and nodule dry weight.

Protective effect of a 50% hydroalcoholic fruit extract of Emblica officinalis against anti-tuberculosis drugs induced liver toxicity.

The present report showed the hepatoprotective property of a 50% hydroalcoholic extract of the fruits of Emblica officinalis (fruit) (EO-50) against antituberculosis (anti-TB) drugs-induced hepatic injury. The biochemical manifestations of hepatotoxicity induced by rifampicin (RIF), isoniazid (INH) and pyrazinamide (PZA), either given alone or in combination were evaluated. In vitro studies were done on suspension cultures of rat hepatocytes while sub-acute studies were carried out in rats. The hepatoprotective activity of EO-50 was found to be due to its membrane stabilizing, antioxidative and CYP 2E1 inhibitory effects.

Bilateral single session ureteroscopy for ureteral calculi : is it safe and effective

Objectives: To determine the feasibility; safety and success rate of bilateral single session rigid retrograde ureteroscopy (URS) for bilateral ureteral calculi. Patients and Methods: Thirty-five patients underwent bilateral single session ureteroscopic calculus removal. Results: Out of 70 renal units in 35 patients treated; clearance of the calculus was successful in the first session of ureteroscopy in 63 (90). A total of 28 patients (80) were completely rendered stone-free bilaterally in one operative session. Two patients needed a second session of URS; while five required ESWL for residual or migrated stone fragments. No major procedure-related complications were encountered in any of our patients. Conclusion: Bilateral single-session rigid URS for ureteral calculi is feasible; safe and effective. There is no significant increase in ureteroscopy-related complications. It spares the patients a second anaesthesia and a second procedure and; thus; reduces the total hospital stay; total expenditure and enables the patient to resume work earlier

Relationship between serum growth hormone binding protein levels and height in young men.

The biochemical mediators responsible for variations in stature among normal subjects are largely unknown. To obtain some initial information about potential endocrine factors, we measured the serum concentrations of GH, IGF-1, IGFBP-3 and GHBP in healthy young men shorter than 159 cm and taller than 187 cm. We studied 14 volleyball and basketball players (tall group), and 14 jockey students from a horse racetrack (short group). A careful medical history was taken, including dietary intake, and physical examination with special attention to the possible presence of genetic stigmata was performed. Serum prealbumin was determined as an index of nutritional status. A buccal smear was performed to exclude Klinefelter's syndrome. The BMI and serum prealbumin levels were comparable in both groups of individuals. The nutritional survey, however, revealed that the tall subjects had a higher intake of calories (42.2+/-11.2 vs. 30.1+/-15.15 kcal/kg, p<0.05), and protein (1.5+/-0.6 vs. 0.8+/-0.4 mg/kg, p<0.01). Serum concentrations of GHBP did not differ in the two groups (0.95+/-0.37 nmol/l in the tall, and 0.95+/-0.53 nmol/l in the short group), and did not correlate with height, serum IGF-I levels, or BMI. We observed a significant difference in the serum concentrations of IGF-I in the two groups of individuals (42.02+/-9.37 nmol/l in the tall and 31.79+/-3.18 nmol/l in the short group, p<0.05), and this growth factor showed a positive correlation with height (r = 0.5, p<0.01). These preliminary findings suggest that final height differences in young men do not appear to be mediated by variations in GHBP concentrations.

Long-acting peptidomimergic control of gigantism caused by pituitary acidophilic stem cell adenoma.

Gigantism is caused by GH hypersecretion occurring before epiphyseal long bone closure and usually is associated with pituitary adenoma. A 15-yr-old female patient presented with accelerated growth due to a large pituitary tumor that was surgically resected to relieve pressure effects. Second surgery to remove residual tumor tissue was followed by administration of octreotide LAR, a long-acting depot somatostatin analog, together with long-acting cabergoline. Height was over the 95th percentile, with evidence of a recent growth spurt. Serum GH levels were more than 60 ng/mL (normal, <10 ng/mL) with no suppression to 75 g oral glucose, and serum PRL (>8,000 ng/mL; normal, <23 ng/mL) and insulin-like growth factor I levels (845 ng/mL; age-matched normal, 242-660 ng/mL) were elevated. Histology, immunostaining, and electron microscopy demonstrated a pituitary acidophil stem cell adenoma. Tumor tissue expressed both somatostatin receptor type 2 and dopamine receptor type 2. The Gs alpha subunit, GHRH receptor, and MEN1 genes were intact, and tumor tissue abundantly expressed pituitary tumor transforming gene (PTTG). Serum GH and PRL levels were controlled after two surgeries, and with continued cabergoline and octreotide LAR GH, PRL, and insulin-like growth factor I levels were normalized. In conclusion, administration of long-acting somatostatin analog every 4 weeks in combination with a long-acting dopamine agonist biweekly controlled biochemical parameters and accelerated growth in a patient with gigantism caused by a rare pituitary acidophil stem cell adenoma.

Pituitary hypoplasia in patients with a mutation in the growth hormone-releasing hormone receptor gene.

BACKGROUND AND PURPOSE: Several anatomic abnormalities of the pituitary gland have been described as occurring in association with congenital growth hormone deficiency, including hypoplasia of the adenohypophysis, truncation of the pituitary stalk, and ectopia of the neurohypophysis. Their pathogenesis, however, is obscure. Normal pituitary development is dependent on the sequential expression of a series of ontogenetic factors. Growth hormone-releasing hormone (GHRH) is known to stimulate somatotroph proliferation, and a dwarf mouse model with a mutant GHRH receptor, the "little mouse," has a small anterior pituitary due to hypoplasia of the somatotrophs. We recently described the human homolog of the little mouse (dwarfism of Sindh), caused by a homozygous nonsense mutation in the GHRH receptor gene in a Pakistani kindred. We investigated MR imaging characteristics to gain information regarding the potential role of GHRH in human pituitary organogenesis. METHODS: MR images of the head were obtained of four affected male patients (age range, 22-29 years). Maximal anterior pituitary dimensions were determined from sagittal and coronal images, and pituitary volumes were estimated from cubic and ellipsoid formulae. The measurements were compared with normative values matched for age and sex. RESULTS: The adenohypophysis was small in each of the four patients. The maximal height for the anterior pituitary was 3 mm in three patients and 2 mm in one (mean +/- SD, 2.75 +/- 0.5 mm), which is significantly (P < .001) less than the expected height of 5.6 +/- 1.0 mm for men in this age group. Estimates of anterior pituitary volume in the patients ranged from 75 to 124 mm3 (104 +/- 21 mm3), which corresponds to 35% to 52% of the normal mean volume corrected for small head size (P < .005). No other cranial abnormalities were identified. CONCLUSION: We describe significant hypoplasia of the adenohypophysis occurring in four dwarfs with a nonsense mutation in the GHRH receptor. In addition to isolated growth hormone deficiency and severe dwarfism, affected patients have anterior pituitary hypoplasia, presumably due to somatotroph maldevelopment. Resistance to GHRH explains the hypoplasia of the adenohypophysis--a feature that contributes to growth hormone deficiency in this syndrome. This is one of the few instances in which the molecular basis of pituitary dysmorphogenesis has been identified.

Appraisal of growth hormone (GH) secretion: evaluation of a composite pharmacokinetic model that discriminates multiple components of GH input.

Criteria for a diagnosis of GH deficiency include inadequate GH secretion as assessed by provocative testing. The changes in serum GH concentration in such tests, however, do not uniformly predict treatment responses. We questioned whether the changes in serum GH have a uniform dependence among subjects on the mass of secreted GH. We simulated spontaneous GH secretory events with bolus infusions of recombinant human GH (rhGH) in 15 somatostatin-infused adult subjects. Maximum serum GH responses, the GH areas under the curve, and GH mass calculated from deconvolution techniques are all indexes of GH secretion influenced by GH clearance and distribution volume. In this group, these indexes showed a nonuniform dependence on the known GH dose. Despite somatostatin infusion, we found evidence for low level basal GH secretion with oscillatory characteristics that may have influenced the GH concentration dependence on GH dose. We then developed and evaluated a new pharmacokinetic model to account for pulsatile, basal, and oscillatory inputs to the serum GH concentration profile. The new model is comprised of three terms. The first describes plasma GH concentrations from exogenous administration of rhGH according to a one- or a two-compartment model. The second term accounts for basal GH secretion. The third is a cosinor function that describes the oscillatory pattern of basal GH. The composite pharmacokinetic model predicted plasma GH concentrations well (r2 = 0.88-0.97); pharmacokinetic and cosinor parameters had high precision and narrow 95% confidence intervals. The pharmacokinetic parameters were stable and independent. The mean values and coefficients of variance (SD/mean) of GH pharmacokinetic parameters in our 15 subjects were: clearance, 0.236 L/min (24%); volume of distribution, 3.46 L (30%); and terminal half-life, 12.3 min (37%). The values for the cosinor parameters were: basal concentration, 0.22 ng/mL (85%); amplitude, 0.758 (50%); cycle, 121 min (27%); and time shift (acrophase), 60.3 min (53.6%). During the 9-h study, clearance decreased from 0.259 +/- 0.09 to 0.214 +/- 0.06 L/min (P < 0.03), and basal concentration increased from 0.20 +/- 0.22 to 0.33 +/- 0.33 ng/mL (P < 0.5). We conclude that our model can provide useful estimates of GH pharmacokinetics in the presence of basal, oscillating, endogenous concentrations without administering a dose of radiolabeled GH. The substantial inter- and intrasubject variance in pharmacokinetic parameters between subjects negates the assumption of a uniform relationship between GH secretion and serum GH concentration and detracts from the utility of a GH concentration cut-off point in GH testing. These findings have implications to the valid appraisal of GH deficiency states, selection of rhGH treatment candidates, and physiological regulation of the GH axis.

Familial dwarfism due to a novel mutation of the growth hormone-releasing hormone receptor gene.

Isolated growth hormone (GH) deficiency (IGHD) is a rare cause of short stature. The same mutation of the gene encoding the growth hormone-releasing hormone receptor (GHRHR) has been identified as the basis for IGHD in three families from the Indian subcontinent. The prevalence and heterogeneity of defects in the GHRHR gene are not known. Twenty-two dwarf members of a large, extended kindred containing at least 105 affected members with autosomal recessive short stature underwent extensive endocrine evaluation, which confirmed markedly reduced or undetectable serum concentrations of GH that did not increase in response to different stimuli. DNA sequences of the 13 exons and intron-exon boundaries of the GHRHR gene were determined in an index patient. A novel homozygous 5' splice site mutation (G-->A at position +1) in IVS1 was found. Thirty of the affected subjects tested were homozygous for this mutation, and 64 clinically unaffected patients were either heterozygous for the mutation (n = 41, including 9 obligate carriers) or homozygous for the wild-type sequence (n = 23). We describe a novel mutation in the GHRHR gene as cause of dwarfism in the largest kindred with familial IGHD described to date.

Selective lack of growth hormone (GH) response to the GH-releasing peptide hexarelin in patients with GH-releasing hormone receptor deficiency.

The mechanism of the synergistic relationship between GH-releasing peptide (GHRP) and GHRH with respect to GH secretion is poorly understood. We report the response to hexarelin, a potent GHRP, in patients affected with a homozygous mutation in the GHRH receptor gene, with consequent GHRH resistance and GH-deficient dwarfism. This newly described syndrome is the human homolog of the little (lit/lit) mouse. Intravenous administration of hexarelin (2 microg/kg) to four male adult patients (dwarfs of Sindh) resulted in a complete lack of elevation in plasma GH levels (< 1 ng/mL), an at least 50- to 100-fold deviation from the normal response. In contrast, plasma PRL, ACTH, and cortisol levels rose in a normal manner in response to hexarelin. We conclude that an intact GHRH signaling system is critical for GHRPs to exert their effect on GH release, but that the GHRH system is not necessary for the effect of GHRP on PRL and ACTH secretion. Hexarelin (and probably other GHRPs) are not effective agents for the treatment of patients with GHRH resistance due to GHRH receptor deficiency.

Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh.

We report, in detail, a new form of familial dwarfism, including its phenotypic features, hormonal profile, and molecular basis. Following a newspaper report of severe dwarfism in two villages in the province of Sindh, Pakistan, we organized an expedition to study its clinical, genetic, and molecular characteristics. We identified 18 dwarfs (15 male, 3 female), all members of a consanguineous kindred, ranging in age from newborn to 28 yr. Mean height was 7.2 SD below the norm, with mean adult heights of 130 cm for males and 113.5 cm for females. Body proportions and habitus were normal; but head circumference was 4.1 SD, and blood pressure approximately 3 SD below the norm. There was no dysmorphism, no microphallus, and no history of hypoglycemia. Serum GH did not respond to provocative stimuli (GHRH, L-dopa, or clonidine). Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively; mean +/- SD) but rose normally with GH treatment. One affected, dwarfed couple had a son, demonstrating fertility in both sexes. Clinical and endocrinological evidence suggested isolated GH deficiency with a recessive inheritance pattern. The GH-N gene was found to be intact. Linkage analysis of microsatellite chromosomal markers near other candidate genes yielded a high LOD score (6.26) for the GHRH receptor (GHRH-R) locus. DNA sequencing revealed a nonsense mutation (Glu50-->Stop) in the extracellular domain of the GHRH-R. This mutation predicts a severely truncated GHRH-R; it is identical to that recently reported in four patients from two other families. Inheritance is autosomal recessive (chromosome 7p) with a high degree of penetrance. Relatives heterozygous for the mutation had moderately decreased IGF-I levels and slightly blunted GH responses to GHRH and L-dopa, but they showed only minimal or no height deficit. This syndrome represents the human homologue of the little (lit/lit) mouse and closely resembles its phenotype. It demonstrates the absolute requirement of GHRH signaling for pituitary GH secretion and postnatal growth in humans, and its relatively minor (but discernible) biological importance in extrapituitary sites. The syndrome is distinct from other forms of GH deficiency with respect to microcephaly, asymptomatic hypotension, and absence of features such as facial dysplasia, significant truncal obesity, microphallus, or hypoglycemia. Its discovery raises the possibility of milder mutations in the GHRH-R gene as potential causes for partial GH insufficiency and idiopathic short stature.

Blockade of growth hormone receptor shedding by a metalloprotease inhibitor.

GH, an important growth-promoting and metabolic hormone, exerts its biological effects by interacting with cell surface GH receptors (GHRs). The GHR is a single membrane-spanning protein that binds GH via its extracellular domain. The high affinity GH-binding protein (GHBP), which corresponds to a soluble form of the GHR extracellular domain, carries a substantial fraction of the GH in the circulation of various species and probably has a role in modulation of the hormone's bioavailability. Although in rodents, it is believed that the GHBP is largely derived by translation of an alternatively spliced GHR messenger RNA, in humans and rabbits, proteolytic cleavage of the membrane-anchored receptor releases the GHR extracellular domain, which is believed to thereby become the GHBP. In this study, we used human IM-9 lymphocytes and GHR antibodies to study this proteolytic shedding of the GHBP. As determined by immunoblotting with anti-GHR cytoplasmic domain serum, addition of phorbol 12-myristate 13-acetate (PMA; 1 microg/ml) to serum-starved cells led to rapid loss (roughly 60% decline after 1 h; t(1/2) = approximately 5 min) of mature GHRs (115-140 kDa) from either total cell or detergent-soluble extracts. Loss of full-length GHRs was accompanied by accumulation of four proteins (65-68 kDa), each reactive with the cytoplasmically directed antiserum. The pattern of appearance of these GHR ctyoplasmic domain proteins, the electrophoretic and immunological characteristics of which are similar to those of a recombinant rabbit GHR mutant that lacks the extracellular domain, was such that progressively faster migrating forms were evident between 5-60 min of PMA exposure. Treatment with N-ethylmaleimide (NEM; 5 mM), an agent known to cause GHBP shedding from IM-9 cells, promoted a similar rapid loss of full-length GHRs and an accumulation of GHR cytoplasmic domain remnant proteins. PMA-induced, but not NEM-induced, GHR proteolysis was blocked by the protein kinase C inhibitor, GF109203X. Both PMA- and NEM-induced receptor proteolysis were, however, inhibited by the metalloprotease inhibitor, Immunex Compound 3 (minimum effective concentration, 10 microM). Notably, PMA and NEM also promoted shedding of GHBP into the conditioned medium of the cells, as determined by a chromatographic [125I]human GH binding assay; this GHBP shedding was also inhibited by Immunex Compound 3. These results strongly implicate a member(s) of the metalloprotease family as a potential GHBP-generating enzyme.

The Dwarfs of Sindh: severe growth hormone (GH) deficiency caused by a mutation in the GH-releasing hormone receptor gene.

We report the discovery of a cluster of severe familial dwarfism in two villages in the Province of Sindh in Pakistan. Dwarfism is proportionate and occurs in members of a kindred with a high degree of consanguinity. Only the last generation is affected, with the oldest dwarf being 28 years old. The mode of inheritance is autosomal recessive. Phenotype analysis and endocrine testing revealed isolated growth hormone deficiency (GHD) as the reason for growth failure. Linkage analysis for the loci of several candidate genes yielded a high lod score for the growth hormone-releasing hormone receptor (GHRH-R) locus on chromosome 7. Amplification and sequencing of the GHRH-R gene in affected subjects demonstrated an amber nonsense mutation (GAG-->TAG; Glu50-->Stop) in exon 3. The mutation, in its homozygous form, segregated 100% with the dwarf phenotype. It predicts a truncation of the GHRH-R in its extracellular domain, which is likely to result in a severely disabled or non-existent receptor protein. Subjects who are heterozygous for the mutation show mild biochemical abnormalities in the growth hormone-releasing hormone (GHRH)--growth hormone--insulin-like growth factor axis, but have only minimal or no growth retardation. The occurrence of an offspring of two dwarfed parents indicates that the GHRH-R is not necessary for fertility in either sex. We conclude that Sindh dwarfism is caused by an inactivating mutation in the GHRH-R gene, resulting in the inability to transmit a GHRH signal and consequent severe isolated GHD.

A mammalian model for Laron syndrome produced by targeted disruption of the mouse growth hormone receptor/binding protein gene (the Laron mouse).

Laron syndrome [growth hormone (GH) insensitivity syndrome] is a hereditary dwarfism resulting from defects in the GH receptor (GHR) gene. GHR deficiency has not been reported in mammals other than humans. Many aspects of GHR dysfunction remain unknown because of ethical and practical limitations in studying humans. To create a mammalian model for this disease, we generated mice bearing a disrupted GHR/binding protein (GHR/BP) gene through a homologous gene targeting approach. Homozygous GHR/BP knockout mice showed severe postnatal growth retardation, proportionate dwarfism, absence of the GHR and GH binding protein, greatly decreased serum insulin-like growth factor I and elevated serum GH concentrations. These characteristics represent the phenotype typical of individuals with Laron syndrome. Animals heterozygous for the GHR/BP defect show only minimal growth impairment but have an intermediate biochemical phenotype, with decreased GHR and GH binding protein expression and slightly diminished insulin-like growth factor I levels. These findings indicate that the GHR/BP-deficient mouse (Laron mouse) is a suitable model for human Laron syndrome that will prove useful for the elucidation of many aspects of GHR/BP function that cannot be obtained in humans.

Alteration in IGF-I binding in the cerebral cortex and cerebellum of neonatal rats during protein-calorie malnutrition.

Neonatal brain development in the rat is adversely affected by malnutrition. Alterations in tissue binding of IGF-I in the malnourished brain were tested in rat pups from mothers who were fed a 20% protein diet (C) or a 4% protein diet (M) starting from day 21 of gestation and continued throughout suckling. IGF-I binding in both cortex and cerebellum decreased progressively in C and M groups from day 6 to day 13. At day 9, 11, and 13, the binding was significantly greater (p < 0.02) in M compared to C groups. To investigate whether these changes might be related to the alteration in receptor activity, membranes were incubated with 125I-IGF in the presence of excess insulin with or without unlabeled IGF-I. In the absence of insulin, specific IGF-I binding in the M group was increased by 41.8 +/- 13.8% (mean +/- SEM p < 0.05) relative to C group. Insulin produced a consistent but incomplete inhibition of binding in both C and M, of 75% and 67% respectively. In addition, the specific IGF-I binding in the presence of insulin was increased in M group by 70.2 +/- 9.4% relative to C, p < 0.05. To characterize the nature of this binding, cerebral cortical membranes, from both groups, incubated with 125I-IGF-I were cross-linked, and electrophoresed on 6% and 10% SDS-PAGE gels under reducing conditions. Autoradiography of the 6% gel showed two specific bands at 115 kD and 240 kD, consistent with monomeric and dimeric forms of the IGF-I receptor, which were inhibited by excess insulin. In contrast, a 10% gel showed an additional band at 35 kD (IGF-binding protein) that was not inhibited by insulin. In both gels, membrane preparations from the M group showed a heightened intensity of the bands relative to C. The increase in binding protein relative to the receptor suggests a disequilibrium that may limit the availability of exogenous IGF-I to the tissues.

Insulin, somatotropic, and luteinizing hormone axes in lean and obese women with polycystic ovary syndrome: common and distinct features.

The basic tenet of this investigation was that obesity is not a prerequisite in the development of polycystic ovary syndrome (PCOS), as indicated by the fact that 50% of PCOS women are not obese. Further, obesity itself is a disease entity with the common manifestation of insulin resistance/hyperinsulinemia with PCOS. Given recent evidence that insulin and GH may have gonadotropin-augmenting effects, we have determined the common and distinguishing features of neuroendocrine-metabolic dysfunctions of lean [body mass index (BMI), < 23 kg/m2] and obese (BMI, > 30 kg/m2) women with the classical form of PCOS. Insulin sensitivity, as determined by rapid i.v. glucose tolerance testing; 24-h dynamics of insulin/glucose levels, somatotropic [GH/GH-binding protein/insulin-like growth factor I (IGF-I)/IGF-binding proteins (IGFBP)], and LH axes; and their downstream effects on ovarian steroids were simultaneously assessed in eight lean PCOS and eight obese PCOS patients and an equal number of BMI-matched normal cycling controls. Our results show that insulin sensitivity was reduced 50% (P < 0.01) in lean PCOS from that in lean controls. There was a further decrease in obese controls (P < 0.01) and a 2-fold greater reduction (P < 0.001) in obese PCOS than in obese controls, suggesting that insulin resistance (IR) is a common lesion in PCOS, and that obesity contributes an additional component to IR in obese PCOS. Consistent with the degree of IR, the manifestation of compensatory hyperinsulinemia in lean PCOS was incipient, being evident only in response to meals (P < 0.05), and became overt during the 24-h fasting/feeding phases of the day in obese control (P < 0.001) with a 2- to 3-fold greater elevation (P < 0.001) in obese PCOS. An enhanced early insulin response to glucose occurs equally in obese control (P < 0.01) and obese PCOS (P < 0.05), but not in their lean counterparts. Considering the more profound IR and the associated hyperglycemia in obese PCOS, the magnitude of the early insulin release is inadequate, suggesting that beta-cell dysfunction exists in obese PCOS. Remarkable differences in the somatotropic axis were also observed; although 24-h GH pulse frequency and levels of IGF-I and IGFBP-3 were unaltered by either PCOS or obesity, the 24-h mean GH pulse amplitude was increased by 30% (P < 0.01) in lean PCOS in the presence of normal levels of high affinity GHBP and normal GH response to GHRH. In distinct contrast, the somatotropic axis in both obese control and obese PCOS was profoundly modified, with attenuation of GH pulse amplitude (P < 0.001) and GH response to GHRH (P < 0.001), resulting in a state of hyposomatotropinism with a more than 50% reduction (P < 0.001) of 24-h mean GH levels. In addition, GHBP levels were elevated 2-fold and were correlated inversely with GH (r = -0.81) and positively with insulin (r = 0.75) concentrations. IGFBP-I levels were suppressed in both obese groups, with a 4-fold greater reduction in obese PCOS than that in obese controls. Thus, the downstream effects of hyperinsulinemia on the somatotropic axis may include up-regulation of hepatic production of GHBP, suppression of IGFBP-1 (r = 0.82) and sex hormone-binding globulin (r = -0.69) levels, and a more than 3-fold increase in ratios of IGF-I/IGFBP-1 and estradiol-testosterone/sex hormone-binding globulin, thereby increasing their bioavailabilities. In contrast, LH pulsatility was unaffected by obesity alone. An accelerated LH pulse frequency was evident in both lean and obese PCOS (P < 0.001), whereas the mean 24-h LH pulse amplitude was increased in lean (P < 0.001), but not obese, PCOS patients. These events resulted in a 3-fold increase in 24-h mean LH levels in lean PCOS and a 2-fold increase in obese PCOS. Thus, increased LH pulse frequency and augmented LH response to GnRH are characteristic of PCOS, independent of obesity, and the presence of obesity in PCOS is associated with an attenuated LH pulse amplitude, not accounted f

Decline of plasma growth hormone binding protein in old age.

Aging is associated with a progressive decline in GH secretion and serum insulin-like growth factor (IGF)-I levels. This change in the GH-IGF axis is thought to contribute to the changes in body composition associated with aging, such as a loss in lean body mass and an increase in adipose tissue mass. Although the decrease in GH secretion starts in the third decade of life, marked changes in muscle mass and strength become apparent only much later. To assess whether a component of GH resistance supervenes in senescence, we studied plasma GH binding protein (GHBP) levels in 50 normal subjects between the ages of 61 and 98 yr. The GHBP is a soluble, circulating ectodomain of the GH receptor (GHR); its plasma level is thought to reflect GHR levels in tissues and, hence, GH responsivity. GHBP activity in plasma declined progressively between age 60 and 98 yr. The GHBP levels in nonagenarians was about half that of persons aged 60-65. This contrasts with younger adults, where GHBP levels remain relatively stable between the ages of 20 and 60. We conclude that in advanced age. GHBP and, by inference, GHR levels, decrease, which may add an element of GH resistance to the already compromised GH secretion status, thereby further contributing to the changes in body composition and frailty in the elderly.

Growth hormone-binding protein in human lymph.

The high affinity GH-binding protein (GHBP) is a soluble circulating ectodomain of the GH receptor (GHR). In humans, it is thought to be released from the plasma membrane-bound GHR by proteolysis at or near the transmembrane domain. GHBP modulates GH action by 1) intravascular complex formation, and 2) competing with the GHR for ligand in tissues (interstitial complex formation). Little is known about the tissue source(s) of GHBP, the local regulation of GHBP generation, or its concentration in the interstitium. To begin addressing these questions, we studied GHBP levels in peripheral lymph, whose composition approximates that of interstitial fluid. Lymph was collected in 13 healthy adult men from cannulated lymphatic vessels in the calf. Venous and arterial blood samples were collected from the femoral vein and radial artery contemporaneously with lymph collection. Potential GHBP production by endothelial or blood cells was assessed by examining conditioned medium from in vitro cell cultures. GHBP activity was measured by standardized GH binding/column chromatography assay. GHBP was consistently and significantly lower in lymph (mean +/- SD, 4.6 +/- 1.2% GH bound/200 microL) than in venous (14.1 +/- 3.0%) or arterial (14.9 +/- 3.6%) plasma. Conditioned medium from endothelial or blood cell cultures did not contain detectable GHBP. We conclude that the level of GHBP in peripheral lymph is substantially lower than that in the peripheral circulation, and that components of the vasculature are not important sources of GHBP. These findings suggests that 1) the main tissue sources of GHBP in man are the central organs (especially liver); and 2) transcapillary diffusion of GHBP into the interstitial space is restricted.

The evolution of changes in immunoreactive serum insulin-like growth factors (IGFs), IGF-binding proteins, circulating growth hormone (GH) and GH-binding protein as a result of short-term dexamethasone treatment.

Inhibition of growth in man and laboratory animals by glucocorticoid treatment is well recognized, yet we have previously shown that glucocorticoids may paradoxically enhance GH secretion and increase serum insulin-like growth factor (IGF) levels. IGFs circulate bound to high-affinity binding proteins (IGFBPs) which modulate their actions, and circulating GH may be associated with two binding proteins (GHBPs) of which the high-affinity GHBP has been characterized and is structurally identical to the extracellular domain of the GH receptor. We have investigated the time-course of changes in GH, IGFs and their binding proteins induced by glucocorticoid treatment in normal male volunteers (n = 12, age range 22-31 years) sampled at 0800 h daily before and during treatment with dexamethasone (2 mg twice daily) for 5 days. In addition, subjects were sampled at 30-min intervals over 7-h periods (0730-1430 h) during the day prior to dexamethasone (day 0), on day 1 following the first dose of dexamethasone and on day 5 following the last dose of dexamethasone. Mean serum IGF-I rose over the initial 72 h and remained elevated at 96 h (297 +/- 11.5 compared with basal levels of 215.5 +/- 9.3 micrograms/l, P < 0.001) whereas IGF-II levels did not change (472.6 +/- 20.5 vs 450.3 +/- 21.7 micrograms/l, P = 0.97). There was a concomitant rise in serum IGFBP-3 from basal levels of 3.69 +/- 0.23 mg/l to a peak at 5 days of 4.16 +/- 0.21 (P = 0.003 vs day 1).(ABSTRACT TRUNCATED AT 250 WORDS)