Prevalence of neuroendocrine dysfunction in patients recovering from traumatic brain injury.

Although hypopituitarism is a known complication of head injury, it may be underrecognized due to its subtle clinical manifestations. The nonspecific symptoms may be masked by and may contribute to the physical and psychological sequelae of brain trauma. This study examines the prevalence of neuroendocrine abnormalities in patients rehabilitating from traumatic brain injury. Seventy adults (mean age, 31.5 +/- 1.1 yr; range, 18--58; 46 men and 24 women) with traumatic brain injury an average of 49 +/- 8 months before the study (median, 13 months) underwent a series of standard endocrine tests, including serum levels of TSH, free T(4), insulin-like growth factor I, PRL, testosterone (males), and cosyntropin stimulation. Abnormal results of these tests were followed by dynamic tests of gonadotropin, TSH, and GH secretion. Glucagon stimulation testing in 48 subjects revealed GH deficiency (peak, <3 microg/L) in 14.6%. Free T(4) (n = 6; 8.6%), TSH (n = 7; 10%), or both (n = 2; 2.9%) were low in 21.7%, whereas 87% had both TSH and free T(4) below the midnormal level. Basal morning cortisol was below normal in 45.7% of subjects, whereas cosyntropin-stimulated levels were insufficient (peak, <500 nmol/L) in 7.1%. Hypogonadism and hyperprolactinemia were uncommon. In summary, pituitary hormone deficiencies were identified in a substantial proportion of patients with previous brain injury. GH deficiency, found in 15% by glucagon stimulation testing, may compound the physical and psychological complications of traumatic brain injury and interfere with rehabilitation.

Impact of resistance exercise during bed rest on skeletal muscle sarcopenia and myosin isoform distribution.

Because resistance exercise (REx) and bed-rest unloading (BRU) are associated with opposing adaptations, our purpose was to test the efficacy of REx against the effects of 14 days of BRU on the knee-extensor muscle group. Sixteen healthy men were randomly assigned to no exercise (NoEx; n = 8) or REx (n = 8). REx performed five sets of leg press exercise with 80-85% of one repetition maximum (1 RM) every other day during BRU. Muscle samples were removed from the vastus lateralis muscle by percutaneous needle biopsy. Myofiber distribution was determined immunohistochemically with three monoclonal antibodies against myosin heavy chain (MHC) isoforms (I, IIa, IIx). MHC distribution was further assessed by quantitative gel electrophoresis. Dynamic 1-RM leg press and unilateral maximum voluntary isometric contraction (MVC) were determined. Maximal neural activation (root mean squared electromyogram) and rate of torque development (RTD) were measured during MVC. Reductions (P < 0.05) in type I (15%) and type II (17%) myofiber cross-sectional areas were found in NoEx but not in REx. Electrophoresis revealed no changes in MHC isoform distribution. The percentage of type IIx myofibers decreased (P < 0.05) in REx from 9 to 2% and did not change in NoEx. 1 RM was reduced (P < 0.05) by 9% in NoEx but was unchanged in REx. MVC fell by 15 and 13% in NoEx and REx, respectively. The agonist-to-antagonist root mean squared electromyogram ratio decreased (P < 0.05) 19% in REx. RTD slowed (P < 0.05) by 54% in NoEx only. Results indicate that REx prevented BRU-induced myofiber atrophy and also maintained training-specific strength. Unlike spaceflight, BRU did not induce shifts in myosin phenotype. The reported benefits of REx may prove useful in prescribing exercise for astronauts in microgravity.

Setting standards and defining quality of performance in the validation of a standardized-patient examination format.

PURPOSE: To evaluate whether written standards increase the reproducibility of a physician-facilitated station in an objective structured clinical examination (OSCE) designed to assess history, physical-examination, and communication skills. METHOD: The OSCE examination at the University of Texas Medical Branch-Galveston consists of ten eight-minute stations. Six of these stations consist of three History, Physical-examination, Problem-solving, and Plan (HPPP) station pairs. Each existing clinical-problem HPPP station was given to two content experts to develop standards for faculty rating scales appropriate for the evaluation of third-year medical students. Three pairs of faculty members were used to determine interrater reliability by scoring videotapes of three HPPP stations' presentation and problem-solving components. Faculty pairs scored tapes of 15 students without using standards and tapes of 15 students using the standards developed. Differences between the reliabilities without and with the standards were tested for significance using Fisher's R to Z transformation. The reproducibility and standard error of measurement (SEM) were extrapolated for increasing amounts of testing time. The HPPP component scores were also correlated with the written examination scores and preceptors' ratings. Data were obtained from the three HPPP stations used in the 1995-96 internal medicine clerkship SP examination. RESULTS: In all, 196 students completed the OSCE examination. The standards developed improved interrater reliability and reached statistical significance (p < .01) for one HPPP station. Reproducibility for the presentation and problem-solving components of the HPPP stations were > .80 after five hours of testing. The problem-solving component correlated at .37 and .19 with written examinations and with ward grades, respectively. CONCLUSION: The data from this study suggest that standards increase the reproducibility of presentation and problem-solving components of an OSCE to a level as high as, or higher than, that associated with the history, physical-examination, and communication components of traditional standardized-patient examinations.

The somatopause: should growth hormone deficiency in older people Be treated?

Secretion of growth hormone (GH) by the pituitary gland progressively declines beginning in early adult life, a phenomenon which is termed "the somatopause." The observation that many of the changes which occur with advancing age are opposite to the physiologic effects of GH suggests that declining levels of GH and insulin-like growth factor I (IGF-I), the mediator of many of the actions of GH, may be responsible for some of these changes. This article reviews the current understanding of mechanisms underlying the somatopause, the changes of aging which may result from diminished activity of the GH-IGF-I axis, the evidence which suggests that GH "replacement therapy" may reverse these changes, and the risks of treating somatopause with GH replacement.

Functional consequences of the somatopause and its treatment.

The decline in the function of the growth hormone-releasing hormone, growth hormone, insulin-like growth factor (GHRH-GH-IGF) axis has been termed the somatopause. Many of the catabolic sequelae seen in normal aging has been attributed to this decrease in circulating GH and IGF-I. In order to provide hormone replacement therapy for the somatopause, elderly subjects have been treated with GH, IGF-I, or both hormones together. Whereas numerous beneficial effects on body composition, strength, and quality of life have been reported in some studies, other studies have reported only marginal functional improvements. Moreover, it is clear that both hormones can cause significant morbidity.

A TCR binds to antagonist ligands with lower affinities and faster dissociation rates than to agonists.

T lymphocyte activation is mediated by the interaction of specific TCR with antigenic peptides bound to MHC molecules. Single amino acid substitutions are often capable of changing the effect of a peptide from stimulatory to antagonistic. Using surface plasmon resonance, we have analyzed the interaction between a complex consisting of variants of the MCC peptide bound to a mouse class II MHC (Ek) and a specific TCR. Using both an improved direct binding method as well as a novel inhibition assay, we show that the affinities of three different antagonist peptide-Ek complexes are approximately 10-50 times lower than that of the wildtype MCC-Ek complex for the TCR, largely due to an increased off-rate. These results suggest that the biological effects of peptide antagonists and partial agonists may be largely based on kinetic parameters.

Growth hormone deficiency in adults: characteristics and response to growth hormone replacement.

Despite adequate adrenal, gonadal, and thyroid hormone replacement, many adults with hypopituitarism have a recognizable syndrome of weakness and diminished sense of well-being, accompanied by alterations in metabolism and body composition, as well as increased mortality. Short-term treatment with human growth hormone improves many of these abnormalities, but a clear improvement in functional status has yet to be demonstrated. Until such an effect is shown, the use of growth hormone replacement in adults with hypopituitarism remains investigational.

Enhanced T cell maturation and altered lineage commitment in T cell receptor/CD4-transgenic mice.

The two mature subsets of T lymphocytes, CD4+ and CD8+ cells arise from a common progenitor during development in the thymus. The differentiation of this progenitor cell into one of the two mature T cell subsets is determined by the specificity of the alpha beta TCR for MHC class I or class II molecules. Using a line of TCR-transgenic mice expressing an MHC class II-specific TCR, 2B4, we have examined the thymocyte subsets present in a selecting versus a nonselecting MHC background. Our results are consistent with the model that CD4 versus CD8 downregulation occurs stochastically. In an effort to confirm these findings, we examined T cell development in double-transgenic mice expressing high levels of a CD4-transgene plus the 2B4 TCR transgenes. Unlike the findings with MHC class I-specific TCR-transgenic models, peripheral T cells in these mice include a substantial fraction of MHC class II-specific (2B4+) T cells expressing CD8 plus the transgene-encoded CD4. In addition, analysis of both thymocytes and peripheral T cells in these double-transgenic mice indicate that CD4 overexpression also leads to a striking enhancement of T cell maturation in 2B4 TCR-transgenic mice. Together with the studies of others, these data support a stochastic model for CD4 versus CD8 lineage commitment of an MHC class II-specific TCR during T cell development in the thymus.

Interactions of growth hormone and parathyroid hormone in renal phosphate, calcium, and calcitriol metabolism and bone remodeling in postmenopausal women.

The mechanisms underlying the effects of recombinant human growth hormone (rhGH) on vitamin D, mineral, and bone metabolism are not known. We examined whether these effects are mediated by parathyroid hormone (PTH) by measuring renal phosphorus (P) and calcium (Ca) handling, serum calcitriol, and markers of bone turnover for 24 h before and 72 h after an infusion of hPTH(1-34) in eight healthy postmenopausal women at baseline and following short-term (1 week) and sustained (5 weeks) rhGH treatment. On short-term rhGH, serum phosphorus and basal TmP/GFR were unaffected, but the fall in TmP/GFR after hPTH infusion was exaggerated (integrated response: -99.2 +/- 22.3 versus -144.1 +/- 15.0 minute-mg/dl, P = 0.0021). Basal calcitriol levels rose from 115 +/- 17 to 163 +/- 16 pM (P = 0.0002), but the increase in calcitriol following hPTH infusion was unaffected by short-term rhGH. The basal Ca excretion index (CEI) rose from 0.054 +/- 0.005 to 0.073 +/- 0.007 mM (P = 0.0095), but markers of bone turnover were unaffected. With sustained rhGH treatment, serum P (1.47 +/- 0.05 mM), basal TmP/GFR (4.29 +/- 0.24 mg/dl), and basal CEI (0.067 +/- 0.005 mM) were elevated compared with control values, and the PTH-induced lowering of TmP/GFR was again enhanced (-158.7 +/- 22.8 minute-mg/dl, P = 0.0021). Basal calcitriol concentrations returned to control levels (108 +/- 10 pM), but the calcitriol response to hPTH remained unchanged. Markers of bone remodeling were elevated with sustained rhGH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

ACTH-independent massive bilateral adrenal disease (AIMBAD): a subtype of Cushing's syndrome with major diagnostic and therapeutic implications.

A 49-year-old man with classic manifestations of Cushing's syndrome had undetectable levels of ACTH, lack of suppression of hypercortisolism with dexamethasone in doses of 2, 8, or 16 mg per day, bilaterally enlarged adrenal glands on MRI, and bilateral adrenal uptake of iodocholesterol. Preoperative treatment with ketoconazole lowered blood pressure and serum cortisol and produced symptoms of steroid withdrawal. Bilateral adrenalectomy revealed massively enlarged adrenal glands (left: 199 g, right: 93 g). Sequencing of the gene encoding the stimulatory G protein, GS alpha, did not show either of two activating mutations previously reported in patients with McCune-Albright syndrome or acromegaly. Twenty-three previous cases of Cushing's syndrome due to ACTH-independent massive bilateral adrenal disease (AIMBAD) have been reported. AIMBAD may cause confusion in the differential diagnosis of Cushing's syndrome as endocrine testing suggests a unilateral, ACTH-independent process while adrenal imaging demonstrates bilateral abnormalities. Bilateral adrenalectomy is curative and appears to carry little risk of Nelson's syndrome. The pathogenesis of AIMBAD appears to be heterogeneous, as recent reports have demonstrated GIP-mediated hypercortisolism and familial AIMBAD. Transition from Cushing's disease to ACTH-independence is not supported by the available data. Future cases of AIMBAD should be investigated carefully to further elucidate the pathogenesis of this disorder.

The insulin-like growth factor I generation test: resistance to growth hormone with aging and estrogen replacement therapy.

Circulating IGF-I is primarily regulated by growth hormone, but other factors such as nutritional status may also influence IGF-I secretion. The effects of age, gender, and estrogen replacement on responsiveness of serum IGF-I to GH administration have not been directly studied. The high-affinity circulating GH-binding protein (GHBP) has the same structure as the extracellular domain of the GH receptor and may reflect the sensitivity to GH in humans. To examine these issues, we employed an IGF-I generation test in which a single dose of GH (0.1 mg/kg SQ) was administered to 31 healthy adults comprising five groups: young (20-29 years) males (YM), young females in the follicular phase of the menstrual cycle (YF), older (60-69 years) males (OM), older females not on estrogen replacement (OFN), and older females on oral estrogen replacement (OFE). Blood was sampled for IGF-I and GHBP over 72 hours following GH administration. OM had lower peak IGF-I levels (323 +/- 38 vs. 497 +/- 85 micrograms/l, p = 0.0015) and a lower IGF-I response to GH (delta IGF-I: 187 +/- 33 vs. 293 +/- 57 micrograms/l, p = 0.0085) than YM. OFE had lower basal IGF-I (63 +/- 11 vs. 133 +/- 19 micrograms/l, p = 0.0046), peak IGF-I (174 +/- 28 vs. 400 +/- 40 micrograms/l, p = 0.0015), and delta IGF-I (111 +/- 21 vs. 268 +/- 27 micrograms/l, p = 0.0085) than OFN. IGFBP-3 levels were unchanged 24 hours after GH administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Anabolic effects of recombinant insulin-like growth factor-I in cachectic patients with the acquired immunodeficiency syndrome.

The loss of lean body mass accompanying acquired immunodeficiency syndrome (AIDS)-associated cachexia is refractory to current modes of therapy. GH and insulin-like growth factor-I (IGF-I) stimulate protein accretion, but resistance to GH action has been reported in malnutrition and infection. We hypothesized that GH resistance occurs in AIDS-associated cachexia, but that treatment with IGF-I would be anabolic. A single injection of GH produced a smaller increase in circulating IGF-I in 21 patients with AIDS compared to that in 23 age-matched controls (141 +/- 15 vs. 194 +/- 15 micrograms/L; P < 0.02), indicating partial GH resistance. Ten subjects received either low or high dose iv recombinant IGF-I 12 h daily for 10 days. Cumulative nitrogen retention was positive for both dosage groups (low dose, 15.42 +/- 6.37 g; high dose, 3.62 +/- 4.15 g), but a significant increase in daily nitrogen retention occurred only in the low dose group on days 2, 4, 5, 6, and 7. Nitrogen balance and protein turnover (estimated by [13C]leucine and [15N] glycine kinetics) during the final 3 days of treatment were unchanged compared to baseline values, confirming the transient nature of the anabolic response. Repeated administration of IGF-I decreased IGF-binding protein-3 levels, producing lower intrainfusion levels of IGF-I and limiting its therapeutic efficacy. The basal metabolic rate increased with high dose IGF-I and may have contributed to the lack of anabolic effect. We conclude that partial GH resistance occurs in AIDS-associated cachexia. Treatment with low dose recombinant IGF-I produces significant, but transient, nitrogen retention. Alternate routes of IGF-I administration or coadministration with GH may prevent attenuation of IGF-I action.

Coordinate silencing of myeloma-specific genes in myeloma x T lymphoma hybrids.

It has been well-established that Ig genes are transcriptionally silenced when Ig-producing myeloma lines are fused to non-B cells. In the present study, we analyzed the expression of several other myeloma-specific genes in fusions of myelomas with the T lymphoma, BW5147. Seven of the eight genes analyzed behaved coordinately with the Ig loci; they were silent in most myeloma x T hybrids but active in the rare hybrid that retained Ig gene expression. Cloned IgH genes introduced into the two types of hybrids behaved as their endogenous counterparts. The coordinate behavior of these several genes in the panel of "exceptional" and "extinguished" hybrids suggests a central and bimodal switch for alternately activating and de-activating the genetic program of the Ig-secreting plasmacyte. The switch between an active and an inactive transcriptional state involves, at some level, a change in the methylation status of the IgH genes. Methylation and transcriptional activity were inversely correlated. In Ig-extinguished hybrids the myeloma-derived locus was methylated de novo, whereas in the rare Ig-expressing hybrid, the T cell-derived locus was demethylated de novo.

Rheumatologic and skeletal changes in acromegaly.

The anabolic functions of growth hormone (GH) and insulin-like growth factor-I (IGF-I) in cartilage and bone metabolism are important in the normal physiology of these tissues. The effects of chronic elevation of GH and IGF-I levels on bony structures produce the typical physical changes associated with acromegaly, whereas the effects on cartilage result in arthropathy, which is usually degenerative. This article presents an overview of the physiologic roles of GH and IGF-I in cartilage and bone metabolism, the clinical features of the degenerative arthropathy and other rheumatologic syndromes associated with acromegaly, effects of acromegaly on bone and mineral metabolism, and an unusual bone disease that is occasionally associated with acromegaly, the McCune-Albright syndrome.

Growth hormone therapy in the elderly: implications for the aging brain.

Growth hormone (GH) secretion declines during normal aging, resulting in lower serum insulin-like growth factor (IGF)-I levels. It has been proposed that many of the catabolic changes seen in normal aging, including osteoporosis and muscle atrophy, are in part caused by the decreased action of the GH-IGF-I axis. In addition, patients with GH deficiency have increased overall cardiovascular mortality. Several investigators have initiated GH treatment for elderly patients with relative hyposomatotropinemia. Initial reports suggest that GH can increase muscle mass, improve exercise tolerance, increase REM sleep and cause an enhanced sense of well-being. The basis for neuropsychiatric changes during GH therapy may be due to a direct CNS action of GH itself, to the increased IGF-I secretion which GH elicits, or to enhanced functioning of peripheral organ systems. Long-term studies will determine whether GH or IGF-I can exert a neurotrophic action in the aging brain.