Inactivation of the luteinizing hormone/chorionic gonadotropin receptor by an insertional mutation in Leydig cell hypoplasia.

We previously identified a nonsense mutation (Cys545Stop) in the paternal human LH/CG receptor (hLHR) allele in a family with two 46,XY children afflicted with Leydig cell hypoplasia. This mutation abolished the signal transduction capability of the affected hLHR. We have now examined all coding exons and the transcript of both alleles of the hLHR gene of the affected children. A 33-bp in-frame insertion was found in the maternal hLHR allele. This insertion occurred between nucleotide 54 and 55 and might be the result of a partial gene duplication. Genomic DNA-PCR showed that this defective maternal hLHR allele was inherited by the two affected children. However, examination of the inheritance of the 935-A/G polymorphism of the hLHR by genomic- and RT-PCR indicated that the maternal hLHR allele was not expressed in cultured fibroblasts of the patients. The effect of the in-frame insertion on the biological activity of the hLHR was examined by expressing the mutated hLHR construct, generated by site-directed mutagenesis, in HEK 293 cells. The expression of the mRNA for the mutant hLHR in HEK 293 cells was not affected. Response of cells expressing the mutated hLHR to hCG stimulation was impaired as demonstrated by reduced intracellular cAMP biosynthesis. This change in signal transduction was the result of a profound reduction in hormone binding at the cell surface due to altered expression and processing of the mutated receptor. We conclude that Leydig cell hypoplasia in this family is the result of compound heterozygous loss-of-function mutations of the hLHR gene.

Effects of fasting on the growth plate: systemic and local mechanisms.

Inadequate caloric intake inhibits longitudinal bone growth. This study was designed to investigate the mechanisms responsible for this suppression of growth plate function, focusing on the roles of systemic and local insulin-like growth factor 1 (IGF-1). Five week-old male rabbits were fasted for 48 h. Fasting significantly decreased proximal tibial growth velocity and growth plate width (both proliferative and hypertrophic zones). During the fast, systemic IGF-1 production was down-regulated. Serum IGF-1 levels and hepatic IGF-1 messenger RNA (mRNA) levels decreased despite increased GH levels. Serum levels of GH binding protein (a circulating fragment of the GH receptor) and hepatic GH receptor mRNA levels were not significantly changed. In contrast, the local, growth plate IGF-1 system appeared to be up-regulated. Growth plate GH receptor mRNA and IGF-1 mRNA levels were both increased during fasting. We conclude that, in the rabbit, fasting induces a rapid depletion of growth plate chondrocytes and inhibition of longitudinal bone growth. These effects appear to be mediated by systemic endocrine mechanisms; circulating IGF-1 levels are diminished because of hepatic resistance to GH. In contrast, the local, paracrine IGF-1 system in growth plate does not appear to contribute to the growth inhibition but instead appears to be up-regulated by fasting.

A preliminary study of flutamide, testolactone, and reduced hydrocortisone dose in the treatment of congenital adrenal hyperplasia.

Treatment outcome in congenital adrenal hyperplasia is often suboptimal due to hyperandrogenism, treatment-induced hypercortisolism, or both. As a new approach, we hypothesized that the effects of androgen could be blocked by an antiandrogen (flutamide) and an inhibitor androgen to estrogen conversion (testolactone), thus allowing the hydrocortisone dose to be reduced. We conducted a short term pilot study in 12 children with congenital adrenal hyperplasia in a randomised cross-over open design to determine whether flutamide, testolactone, reduced hydrocortisone dose, and fludrocortisone are more effective than hydrocortisone and fludrocortisone treatment in normalizing linear growth, weight gain, and bone maturation. Each regimen was administered for 6 months, with a 3-month washout period, consisting of hydrocortisone and fludrocortisone treatment, between regimens. Compared to hydrocortisone and fludrocortisone treatment, the regimen of flutamide, testolactone, reduced hydrocortisone dose (from 12.9 to 7.9 mg/m2 day), and fludrocortisone produced an increase in plasma 17-hydroxyprogesterone levels (P < 0.05) and a decline in urinary cortisol (P < 0.01), linear growth rate (-0.9 +/- 0.5 vs. 1.4 +/- 0.6 SD U; P = 0.003), weight velocity (-0.80 +/- 4.0 vs 0.6 +/- 0.4 SD U; P = 0.01), and bone maturation (0.6 +/- 0.6 vs. 1.4 +/- 0.9 yr bone age/yr chronological age; P = 0.02). Although no important adverse effects were observed, the known potential for flutamide-induced hepatotoxicity made frequent monitoring essential. We conclude that the regimen of flutamide, testolactone, reduced hydrocortisone does, and fludrocortisone improve the short term control of growth and bone maturation in children with congenital adrenal hyperplasia. Long term studies are required to determine whether this approach can improve these children's growth and development.

Heterogeneity of activating mutations of the human luteinizing hormone receptor in male-limited precocious puberty.

Male-limited precocious puberty (MPP) is a gonadotropin-independent disorder that occurs sporadically or is inherited in an autosomal dominant, male-limited pattern. Recent studies have identified constitutively activating missense mutations in the human luteinizing hormone receptor (hLHR) gene leading to Leydig cell activation and precocious puberty. Patients with sporadic MPP (SMPP) or with different ethnic backgrounds appear to have a greater likelihood of having novel mutations. In the current study we examined genomic DNA from two unrelated cases of SMPP of African-American descent for novel mutations of the hLHR gene. A heterozygous A to C transversion at nucleotide 1723 resulting in substitution of Leu for lle575 in transmembrane helix 6 was identified. Human embryonic kidney cells transfected with cDNA for the mutant hLHR-I575L, created by polymerase chain reaction-based mutagenesis of the wild-type (hLHR-wt) cDNA, exhibited increased basal levels of cAMP production in the absence of agonist, indicating constitutive activation. Surface expression of hLHR-I575L, as reflected by human chorionic gonadotropin binding, was diminished compared to hLHR-wt, while agonist affinity was unaffected. With the exception of two polymorphic bases, no mutation was identified within the coding sequence of the hLHR in the second case of SMPP. We conclude that I575L is a unique constitutively activating mutation that impairs cell surface expression of the receptor but does not alter agonist affinity. Furthermore, mutations of the hLHR gene causing SMPP are highly heterogeneous and may be found in regions other than exon 11 of the hLHR. Last, patients with MPP from different ethnic backgrounds are likely to have novel mutations.

Compound heterozygous mutations of the luteinizing hormone receptor gene in Leydig cell hypoplasia.

The human LH receptor (hLHR) is a member of the G protein-coupled receptors characterized by the presence of seven-transmembrane (TM) helices. Inactivating mutations of the hLHR lead to Leydig cell hypoplasia (LCH), a form of male pseudohermaphroditism resulting from the failure of fetal testicular Leydig cell differentiation. We have identified three mutations of the hLHR in a patient with LCH: deletion of exon 8 (delta Exon 8), A872G transition resulting in Asn291Ser substitution in the extracellular domain, and C1847A transversion resulting in Ser616Tyr substitution in the seventh TM helix. Nucleotide sequencing, gene dosage, and allele-specific amplification analyses revealed that exon 8 deletion and the two missense mutations are present in different alleles of the hLHR. Constructs of mutated hLHR (hLHR-delta Exon8, hLHR-872/1847, hLHR-1847, and hLHR-872) were used to transfect 293 cells, and the properties of the hLHR expressed were examined. Ligand-binding assays failed to detect the expression of hLHR-delta Exon8. Transfectants expressing hLHR-872/1847 demonstrated greatly reduced ligand binding and ligand-induced cAMP accumulation in comparison to those expressing wild type hLHR. Similar reduction in cAMP accumulation was observed in transfectants expressing hLHR-1847, but not hLHR-872 alone. These findings suggest that, in addition to the 7-TM helices, the polypeptide encoded by exon 8 plays an important role in LHR expression and signal transduction. On the other hand, glycosylation of Asn291 may not be critical for these activities. These results also establish that LCH can result from impaired signal transduction due to compound heterozygous mutations. Implications of these mutations on structure-function relationship of the hLHR and the genotype-phenotype correlation in LCH are discussed.

Mutations in the Ca(2+)-sensing receptor gene cause autosomal dominant and sporadic hypoparathyroidism.

Parathyroid hormone secretion is negatively regulated by a 7-transmembrane domain, G-protein coupled Ca(2+)-sensing receptor. We hypothesized that activating mutations in this receptor might cause autosomal dominant hypoparathyroidism (ADHP). Consistent with this hypothesis, we identified, in two families with ADHP, heterozygous missense mutations in the Ca(2+)-sensing receptor gene that cosegregated with the disorder. None of 50 normal controls had either mutation. We also identified a de novo, missense Ca(2+)-sensing receptor mutation in a child with severe sporadic hypoparathyroidism. The amino acid substitution in one ADHP family affected the N-terminal, extracellular domain of the receptor. The other mutations involved the transmembrane region. Unlike patients with acquired hypoparathyroidism, patients with these mutations had hypercalciuria even at low serum calcium concentrations. Their greater hypercalciuria presumably reflected activation of Ca(2+)-sensing receptors in kidney cells, where the receptor negatively regulates calcium reabsorption. This augmented hypercalciuria increases the risk of renal complications and thus has implications for the choice of therapy.

Testicular adrenal rest tissue in congenital adrenal hyperplasia: findings at Gray-scale and color Doppler US.

PURPOSE: To study the ultrasound (US) features of scrotal adrenal rest tissue in congenital adrenal hyperplasia (CAH). MATERIALS AND METHODS: Gray-scale and color Doppler US examinations were performed of scrotal masses in eight patients. The masses were evaluated for size, location, echogenicity, sound attenuation, and vascularity. RESULTS: Seventeen intratesticular masses and one extratesticular mass were examined. All were hypoechoic except for one intratesticular mass that contained hyperechoic areas. Six masses demonstrated sound attenuation. The mediastinum testis was found in the center of 11 of the 17 intratesticular masses. At color Doppler US, six masses were hypervascular, seven were isovascular, and five were hypovascular relative to the normal testicle. All intratesticular masses contained vascular structures that entered them from the normal testis without change in course or caliber. Eleven masses showed a spoke-like pattern of converging vessels. CONCLUSION: The US features of scrotal adrenal rests assist diagnosis of CAH.

Thyroid abnormalities in children infected with human immunodeficiency virus.

OBJECTIVE: To study thyroid function in children infected with human immunodeficiency virus (HIV) and determine whether there are correlates of thyroid dysfunction with disease progression. STUDY DESIGN: Total and free thyroxine, triiodothyronine, reverse triiodothyronine, thyrotropin, and thyroxine binding globulin (TBG) were measured in 167 children with HIV infection (age, 1 to 19 years; mean, 9.15 years). SETTING: Pediatric Branch, National Cancer Institute. RESULTS: Free thyroxine was at or below the lower limit of normal (normal, 1.0 to 1.9 ng/dl) in 18% of the children; thyrotropin and TBG levels were above the normal range in 31% and 30%, respectively. There was an inverse correlation between CD4+ cell count and thyrotropin, and between CD4+ cell count and TBG. No correlation was found between thyroid function and other disease symptoms or medications. CONCLUSION: These findings indicate that thyroid abnormalities occur more frequently in children with HIV infection than was previously reported, have a different profile from the thyroid abnormalities associated with other chronic disease conditions, and correlate with disease progression.

Ligand-independent hormone secretion.

The secretion of many hormones is regulated by extracellular signals, such as hormones, growth factors, neurotransmitters, and ions, that mediate signal transduction via a G protein-coupled pathway. Three components comprise the G protein-coupled pathway: the G protein-coupled receptor, the G protein, and the effector. G protein-coupled receptors allow cells to respond to external stimuli and comprise a large superfamily with hundreds of members. G proteins function as signal transducers between ligand-bound receptors and intracellular effectors. G protein-regulated effectors include enzymes of second messenger metabolism, such as adenylyl cyclase, phospholipase C, cyclic GMP phosphodiesterase, and ion channels. Abnormalities in any of these three components alter signal transduction and can lead to human disease. For example, mutations of G protein-coupled receptors that promote G protein activation in the absence of an agonist cause retinitis pigmentosa, hyperthyroidism due to hyperfunctioning thyroid adenomas and thyroid hyperplasia, male-limited precocious puberty, and hypocalcemia. Human disorders attributed to constitutively activating mutations of the alpha subunit of Gs include the McCune-Albright syndrome, adrenocorticotropic hormone-independent Cushing's syndrome, and functional endocrine tumors.

A nonsense mutation of the human luteinizing hormone receptor gene in Leydig cell hypoplasia.

Leydig cell hypoplasia (LCH) is a form of male pseudohermaphroditism in which Leydig cell differentiation and testosterone production are impaired. This report describes the first case of a nonsense mutation (A1635C) in exon 11 of the human luteinizing hormone receptor (hLHR) gene in two sisters with LCH. This mutation causes loss of function of the receptor by introducing a stop codon at residue 545 in transmembrane helix 5 of the hLHR. Surface expression of the truncated hLHR (hLHR-t545) in human embryonic kidney cells stably transfected with cDNA encoding hLHR-t545 was diminished compared to the wild-type hLHR and hCG-induced cAMP accumulation was impaired. These results establish that single base mutations in exon 11 of the hLHR gene can produce inactivation as well as activation of the hLHR. Furthermore, they demonstrate that functional domains between transmembrane helix 5 and the C-terminal cytoplasmic tail of the hLHR are required for normal cell surface expression of the receptor and signal transduction.

Genetic heterogeneity of constitutively activating mutations of the human luteinizing hormone receptor in familial male-limited precocious puberty.

Genomic DNA from 32 unrelated families with male-limited precocious puberty was examined for the previously described Asp-578-->Gly, Met-571-->Ile, and Thr-577-->Ile mutations in transmembrane helix 6 of the human luteinizing hormone receptor (hLHR). Twenty-eight families had the inherited form of the disorder, and of these, 24 were found to have the Asp-578-->Gly mutation. Four additional mutations were found among the remaining four families with the inherited form and in four sporadic cases of the disorder: an A-->C transversion resulting in substitution of leucine for Ile-542 in the fifth transmembrane helix, an A-->G transition resulting in substitution of glycine for Asp-564 in the third cytoplasmic loop, a G-->T transversion resulting in substitution of tyrosine for Asp-578 in the sixth transmembrane helix, and a T-->C transition resulting in substitution of arginine for Cys-581 in the sixth transmembrane helix. Human embryonic kidney cells transfected with cDNAs for each of the mutant hLHRs, created by PCR-based mutagenesis of the wild-type hLHR cDNA, exhibited increased levels of basal cAMP production in the absence of agonist, indicating constitutive activation of the mutation hLHRs. Three of the additional mutations had specific features: Ile-542-->Leu and Cys-581-->Arg appeared ligand-unresponsive, whereas Asp-578-->Tyr appeared to correlate genotype with phenotype. We conclude that the region spanning nt 1624-1741 of exon 11 is a hotspot for heterogeneous point mutations that constitutively activate the hLHR and cause male-limited precocious puberty.

A constitutively activating mutation of the luteinizing hormone receptor in familial male precocious puberty.

Familial male precocious puberty (FMPP) is a gonadotropin-independent disorder that is inherited in an autosomal dominant, male-limited pattern. Affected males generally exhibit signs of puberty by age 4. Testosterone production and Leydig cell hyperplasia occur in the context of prepubertal levels of luteinizing hormone (LH). The LH receptor is a member of the family of G-protein-coupled receptors, and we hypothesized that FMPP might be due to a mutant receptor that is activated in the presence of little or no agonist. A single A-->G base change that results in substitution of glycine for aspartate at position 578 in the sixth transmembrane helix of the LH receptor was found in affected individuals from eight different families. Linkage of the mutation to FMPP was supported by restriction-digest analysis. COS-7 cells expressing the mutant LH receptor exhibited markedly increased cyclic AMP production in the absence of agonist, suggesting that autonomous Leydig cell activity in FMPP is caused by a constitutively activated LH receptor.

Sex differences in sensitivity of the hypothalamic-pituitary-adrenal axis.

Two studies examined sex differences in responsiveness of the hypothalamic-pituitary-adrenal cortical axis, a major component of the stress response. The first measured pituitary-adrenal responses to ovine corticotropin-releasing hormone (oCRH) in 24 health men and 19 healthy women. Plasma adrenocorticotropin hormone (ACTH) response to oCRH were significantly greater among women than among men. In contrast, cortisol concentrations were similar in both groups, though elevations were more prolonged in women. Differences in corticotropin-releasing activity between men and women may help account for these findings; such differences in central components of the stress response might play a role in the known epidemiological differences in diseases of stress system dysregulation between men and women.

Treatment of familial male precocious puberty with spironolactone, testolactone, and deslorelin.

Combined antiandrogen (spironolactone) and aromatase inhibitor (testolactone) are effective for the short term treatment of familial male precocious puberty. During this therapy, plasma testosterone levels remain in the adult range, since spironolactone blocks the testosterone receptor without significantly affecting plasma testosterone levels. After our initial 18-month pilot study, we continued to treat eight boys with the combined therapy for 2.0-4.2 yr. During this time all boys exhibited a pubertal rise in gonadotropin secretion and a diminishing response to treatment, which was manifested by the recurrence of clinical features of puberty and an increase in the bone maturation rate (P < 0.05). Addition of the LHRH agonist deslorelin (4 micrograms/kg.day, sc) to the combined therapy decreased peak LH, plasma testosterone, bone maturation rate, and growth velocity (P < 0.05) over the next year. We conclude that the rise in gonadotropin levels during central activation of hypothalamic LHRH secretion in boys with familial male precocious puberty causes a partial escape from the combined effect of spironolactone and testolactone. The addition of deslorelin to the combined therapy appears to restore the control of puberty in this setting.

Evidence for impaired activation of the hypothalamic-pituitary-adrenal axis in patients with chronic fatigue syndrome.

Chronic fatigue syndrome is characterized by persistent or relapsing debilitating fatigue for at least 6 months in the absence of a medical diagnosis that would explain the clinical presentation. Because primary glucocorticoid deficiency states and affective disorders putatively associated with a deficiency of the arousal-producing neuropeptide CRH can be associated with similar symptoms, we report here a study of the functional integrity of the various components of the hypothalamic-pituitary-adrenal axis in patients meeting research case criteria for chronic fatigue syndrome. Thirty patients and 72 normal volunteers were studied. Basal activity of the hypothalamic-pituitary-adrenal axis was estimated by determinations of 24-h urinary free cortisol-excretion, evening basal plasma total and free cortisol concentrations, and the cortisol binding globulin-binding capacity. The adrenal cortex was evaluated indirectly by cortisol responses during ovine CRH (oCRH) stimulation testing and directly by cortisol responses to graded submaximal doses of ACTH. Plasma ACTH and cortisol responses to oCRH were employed as a direct measure of the functional integrity of the pituitary corticotroph cell. Central CRH secretion was assessed by measuring its level in cerebrospinal fluid. Compared to normal subjects, patients demonstrated significantly reduced basal evening glucocorticoid levels (89.0 +/- 8.7 vs. 148.4 +/- 20.3 nmol/L; P less than 0.01) and low 24-h urinary free cortisol excretion (122.7 +/- 8.9 vs. 203.1 +/- 10.7 nmol/24 h; P less than 0.0002), but elevated basal evening ACTH concentrations. There was increased adrenocortical sensitivity to ACTH, but a reduced maximal response [F(3.26, 65.16) = 5.50; P = 0.0015). Patients showed attenuated net integrated ACTH responses to oCRH (128.0 +/- 26.4 vs. 225.4 +/- 34.5 pmol/L.min, P less than 0.04). Cerebrospinal fluid CRH levels in patients were no different from control values (8.4 +/- 0.6 vs. 7.7 +/- 0.5 pmol/L; P = NS). Although we cannot definitively account for the etiology of the mild glucocorticoid deficiency seen in chronic fatigue syndrome patients, the enhanced adrenocortical sensitivity to exogenous ACTH and blunted ACTH responses to oCRH are incompatible with a primary adrenal insufficiency. A pituitary source is also unlikely, since basal evening plasma ACTH concentrations were elevated. Hence, the data are most compatible with a mild central adrenal insufficiency secondary to either a deficiency of CRH or some other central stimulus to the pituitary-adrenal axis. Whether a mild glucocorticoid deficiency or a putative deficiency of an arousal-producing neuropeptide such as CRH is related to the clinical symptomatology of the chronic fatigue syndrome remains to be determined.

Adrenal androgen secretion in postadolescent acne: increased adrenocortical function without hypersensitivity to adrenocorticotropin.

Basal and ACTH-stimulated plasma levels of cortisol, delta 4-androstenedione, and dehydroepiandrosterone (DHEA) were measured in a group of 11 female patients with postadolescent acne resistant to or relapsing after conventional therapy and in a group of 10 normal women without acne or hirsutism. Each patient received, in a blinded random fashion, a series of 5 1-h ACTH tests. For each test a different dose of ACTH-(1-24) was administered, ranging from 0-1 microgram/kg, given as an iv bolus. Blood samples were collected 0, 10, 30, and 60 min after ACTH bolus injection. Patients with acne had slightly higher concentrations of basal cortisol, delta 4-androstenedione, and DHEA than normal controls (P less than 0.05). After ACTH-(1-24) stimulation, the same patients had greater peak and time-integrated DHEA concentrations (P less than 0.03). The ED50 values of the cortisol dose-response curves were similar in patients and normal women (P less than 0.05), suggesting that there are no differences in the sensitivity of the adrenal cortex to ACTH between the acne patients and the controls studied. The ratio of DHEA to cortisol response was significantly elevated in women with acne compared to that in control women, suggesting some preponderance of the delta 5 pathway of steroidogenesis in acne (P less than 0.05). These findings of basal and ACTH-stimulated hypersecretion of delta 5-androgens in patients with postaldolescent acne are consistent with an increased volume of androgen-secreting tissue, rather than hypersensitivity of the adrenal zona reticularis to ACTH.