Failure of antibody response to polysaccharide antigen in treated panhypopituitary adults.

Although pituitary hormones are known to affect immune function, treated hypopituitarism is not a recognized cause of immune deficiency in humans. We set out to assess integrity of baseline and stimulated immune function in severely hypopituitary adults. Twenty-one panhypopituitary adults (group 1), on stable pituitary replacement including growth hormone, and 12 healthy volunteers (group 2) were studied. Lymphocyte subsets, pneumococcal antibody levels pre- and 1 month after polysaccharide vaccination, T cell numbers and in-vitro interferon (IFN)-gamma response were studied. There were no significant differences in T cell numbers or IFN-gamma secretion. B cell numbers were lower in group 1, especially those with low prolactin levels. Independent of this finding, nine of 21 patients in this group had low antibody response to polysaccharide antigen. This was most striking in those with low insulin-like growth factor 1 levels and appeared to be independent of the use of anti-convulsants or corticosteroid replacement. Significant humoral immune deficiency is seen in panhypopituitarism and may contribute to morbidity.

Use of a GH receptor antagonist (GHRA) to explore the relationship between GH and IGF-I in adults with severe GH deficiency (GHD).

OBJECTIVE: At diagnosis, approximately 50% of adults with severe GH deficiency (GHD) have an IGF-I within the reference range. It is unclear whether in such patients serum IGF-I levels are regulated by factors other than GH. DESIGN AND PATIENTS: We performed a double-blind, randomized, placebo-controlled, cross-over study to investigate the effect of the GH receptor antagonist - pegvisomant (20 mg daily for 14 days) on GH and IGF-I levels in three cohorts: patients with GHD and a normal IGF-I (NORMS); patients with GHD and a low IGF-I (LOWS) and healthy volunteers (CONS). RESULTS: Pegvisomant decreased IGF-I in CONS and NORMS [158.5 (101-206) vs. 103 (77-125) microg/l, P < 0.01; 124 (81-136) vs. 95 (51-113) microg/l, P < 0.01 respectively], but not in LOWS [31 (< 31-32) vs. 34.5 (< 31-38) microg/l], and this was associated with an increase in mean 24 h GH in CONS [0.49 (0.12-0.89) to 1.38 (0.22-2.45) microg/l (P = 0.03)] and in NORMS [69 (0-320)% from 0.1 (< 0.1-0.13) to 0.17 (0.11-0.42) microg/l (P = 0.03)], but not in the LOWS. The peak GH response to arginine was increased by pegvisomant in CONS and NORMS [6.1 (0.8-9) vs. 20.4 (13.1-28.8) microg/l, P = 0.03; 0.4 (0.1-0.5) vs. 0.5 (0.3-0.6) microg/l, respectively], but not in LOWS. CONCLUSIONS: These data indicate that patients with severe GHD with a normal IGF-I are able to increase GH secretion in response to a pegvisomant-induced fall in IGF-I, whereas those with low IGF-I levels are unable to increase GH secretion. Therefore circulating IGF-I appears to be GH-independent in GHD patients with a low IGF-I, but remains partially GH-dependent in GHD patients with a normal IGF-I.

Optimizing gh therapy in adults and children.

Until the advent of modern neuroradiological imaging techniques in 1989, a diagnosis of GH deficiency in adults carried little significance other than as a marker of hypothalamo-pituitary disease. The relatively recent recognition of a characteristic clinical syndrome associated with failure of spontaneous GH secretion and the potential reversal of many of its features with recombinant human GH has prompted a closer examination of the physiological role of GH after linear growth is complete. The safe clinical practice of GH replacement demands a method of judging overall GH status, but there is no biological marker in adults that is the equivalent of linear growth in a child by which to judge the efficacy of GH replacement. Assessment of optimal GH replacement is made difficult by the apparent diverse actions of GH in health, concern about the avoidance of iatrogenic acromegaly, and the growing realization that an individual's risk of developing certain cancers may, at least in part, be influenced by cumulative exposure to the chief mediator of GH action, IGF-I. As in all areas of clinical practice, strategies and protocols vary between centers, but most physicians experienced in the management of pituitary disease agree that GH is most appropriately begun at low doses, building up slowly to the final maintenance dose. This, in turn, is best determined by a combination of clinical response and measurement of serum IGF-I, avoiding supraphysiological levels of this GH-dependent peptide. Numerous studies have helped define the optimum management of GH replacement during childhood. The recent requirement to measure and monitor GH status in adult life has called into question the appropriateness of simplistic weight- and surface area-based dosing regimens for the management of GH deficiency in childhood, with reliance on linear growth as the sole marker of GH action. It is clear that the monitoring of parameters other than linear growth to help refine GH therapy should now be incorporated into childhood GH treatment protocols. Further research will be required to define the optimal management of the transition from pediatric to adult GH replacement; this transition will only be possible once the benefits of GH in mature adults are defined and accepted by pediatric and adult endocrinologists alike.

Prevalence and consequences of androgen deficiency in young male cancer survivors in a controlled cross-sectional study.

BACKGROUND: Testosterone replacement in hypogonadal males improves body composition, sexual function, and health-related quality of life. Male cancer survivors are at risk of androgen deficiency; however, when and in whom testosterone should be replaced remain unanswered questions. OBJECTIVE: The aim of our study was to define the prevalence of androgen deficiency in this patient group through assessment of testosterone levels and related measures. DESIGN: This was a cross-sectional, observational study of cases and controls. We recruited 176 cancer survivors and 213 controls, aged 25-45 yr. RESULTS: Of cancer survivors, 97% had received chemotherapy and 40% radiotherapy. Cancer survivors had lower total testosterone (tT) levels than controls (mean difference 2.67 nmol/liter; 95% confidence interval 1.58-3.76; P = 0.003), and 24 of 176 (13.6%; 95% confidence interval 9.3-19.5) had a tT less than 10 nmol/liter, which was less than 2.5% centile for controls. Cancer survivors had a greater fat mass, higher fasting insulin and glucose levels, increased fatigue, and reduced sexual function and health-related quality of life. In both cohorts, the tT correlated negatively with insulin levels and negatively with body fat mass; however, the difference in tT between them was independent of fat mass. We measured tT and SHBG and calculated bioavailable testosterone. The changes in calculated bioavailable testosterone were similar to tT. CONCLUSIONS: A significant proportion of young male cancer survivors had a frankly low tT associated with an increased fat mass and insulin level compared with controls. These factors would be predicted to improve in response to testosterone replacement therapy and provide a powerful argument for an interventional study of testosterone therapy in young male cancer survivors.

Defining growth hormone status in adults with hypopituitarism.

The identification of adults with severe growth hormone (GH) deficiency (GHD) is not straightforward. The insulin tolerance test remains the gold standard diagnostic test, although other stimuli such as GH-releasing hormone-arginine are gaining acceptance. Insulin-like growth factor-I has a poor diagnostic sensitivity in adult-onset GHD, but is more useful in the subgroup of adults with childhood-onset GHD. Therapeutic developments include increasing recognition of the need to continue GH therapy beyond final height in young adults with severe GHD on retesting. Consensus guidelines have provided a useful algorithm to identify individuals requiring retesting and the number of tests needed. The concept of partial GHD, recognized by paediatric endocrinologists for many years, is being examined in adults with hypothalamic-pituitary disease. Preliminary evidence suggests that this entity is associated with metabolic and anthropometric abnormalities intermediate between those in severe GHD and in healthy controls. It remains to be seen whether this subgroup will derive benefit from GH therapy. To date, therapeutic benefits of GH have been demonstrated only in adults with severe GHD. It is, therefore, imperative that these individuals are unequivocally identified; the diagnosis becomes more uncertain in the presence of obesity, increasing age, and in the absence of additional pituitary hormone deficits.

Prolactin deficiency is independently associated with reduced insulin-like growth factor I status in severely growth hormone-deficient adults.

BACKGROUND: In adult life, considerable overlap in IGF-I status exists between normal and severely GH-deficient (GHD) subjects defined by conventional dynamic testing of GH secretion. IGF-I is not therefore widely viewed as a reliable diagnostic marker for GHD. Recognized factors influencing serum IGF-I level in GHD include age, gender, timing of onset of GHD, and exogenous estrogen therapy, but these do not fully explain GH/IGF-I discordance in severe GHD. The primary structures of prolactin and GH are closely related. Effects of hypoprolactinemia are not well described in humans, but laboratory studies suggest a role for prolactin in hepatic IGF-I release, possibly through a signal transducer and activator of transcription 5 (STAT5) pathway. The purpose of this study was to evaluate a potential contribution of prolactin to IGF-I status in severely GHD adults. PATIENTS AND METHODS: Using multiple regression analysis techniques, contributions of the following variables to age-adjusted IGF-I sd scores were evaluated in 162 (85 female) GHD adults: gender, timing of onset of GHD, presence or absence of prolactin deficiency, body mass index, number of additional pituitary deficits, and underlying pathology. RESULTS: Childhood onset GHD (P < 0.0001) and presence of prolactin deficiency (P < 0.0001) were independently associated with reduced IGF-I status. The contributions of these parameters to IGF-I sd scores were -2.55 and -2.67, respectively. Gender (P = 0.06), body mass index (P = 0.99), number of additional pituitary deficits (P = 0.64), and underlying pathology (P = 0.06) did not significantly influence IGF-I status. CONCLUSIONS: Prolactin deficiency is independently associated with reduced IGF-I status in hypopituitary adults. It is possible that prolactin deficiency is a surrogate for the degree of severity of GHD, implying a GHD paradigm undetected by conventional GH provocative tests; alternatively, it remains plausible that circulating prolactin contributes to IGF-I release in the absence of GH, possibly through a signal transducer and activator of transcription 5 (STAT5) pathway.

Aetiology, diagnosis, and management of hypopituitarism in adult life.

Hypopituitarism is a complex medical condition associated with increased morbidity and mortality, requires complicated treatment regimens, and necessitates lifelong follow up by the endocrinologist. The causes, clinical features, and the management of hypopituitarism including endocrine replacement therapy are considered in this review article.

Protection of spermatogenesis in rats from the cytotoxic procarbazine by the depot formulation of Zoladex, a gonadotropin-releasing hormone agonist.

The hypothesis that adjuvant treatment designed to produce testicular atrophy would preserve fertility in males receiving cancer chemotherapy was examined in the rat. Testicular atrophy was induced by a depot formulation of Zoladex [D-Ser(Bu(t))6-Aza-Gly10-GnRH], a gonadotropin-releasing hormone (GnRH) analogue. The experiments were conducted in albino Wistar as well as in the piebald variegated rat. Rats received the depot Zoladex formulation 2 weeks before and immediately prior to being treated with four weekly doses of procarbazine (200 mg/kg). Testicular function was evaluated 50 and 90 days after the last procarbazine dose. Procarbazine induced testicular atrophy concomitant with marked germinal cell aplasia in both strains of rat. In the Wistar rat adjuvant treatment with Zoladex caused slight but not significant alleviation of the testicular toxicity of procarbazine. The testicular toxicity of procarbazine was more extensive in the piebald variegated rat, and 50 days after the last procarbazine treatment the testes were small, sperm were absent, and the stem cell index was close to zero. Serum luteinizing hormone (LH) concentrations were raised and testicular LH receptor binding was low in the presence of normal serum and testicular testosterone concentrations, indicating compensated Leydig cell failure. Testicular weight and sperm content, as well as LH receptor binding, were still decreased in rats which received both Zoladex and procarbazine, suggesting that the analogue offered no protection. However, the stem cell index of the seminiferous tubules in the procarbazine-Zoladex-treated rats was not significantly different from vehicle-treated rats, which suggested that recovery from the effects of procarbazine was in progress. Ninety days after the end of procarbazine treatment alone the testes of rats were still atrophied and there was little evidence of active spermatogenesis. Leydig cell failure appeared to have progressed as, in addition to the low testicular LH receptor content and raised serum LH concentration, the prostate and seminal vehicle weights were decreased. The combination of Zoladex treatment with procarbazine was successful in preserving testicular function in the piebald variegated rats as virtually all the functional and morphological parameters of both the seminiferous tubule and the Leydig cell were not significantly different from those of vehicle-treated rats. This study demonstrates for the first time that effective gonadal protection from the toxic effects of procarbazine chemotherapy can be achieved by administration of the depot formulation of the gonadotropin-releasing hormone analogue Zoladex. The results show clearly that complete suppression of spermatogenesis is not a prerequisite for the successful outcome of treatments designed to protect the gonad from cytotoxic chemotherapy.

The characteristics of quality of life impairment in adult growth hormone (GH)-deficient survivors of cancer and their response to GH replacement therapy.

We studied 50 (27 women and 23 men) GH-deficient (GHD) cancer survivors and 47 (24 women and 23 men) GHD patients with pituitary pathologies. All GHD patients were considered for GH replacement on the basis of subjectively poor quality of life (QOL). Primary outcome measures were scores of QOL instruments psychological general well-being schedule (PGWB) and assessment of GH deficiency in adults (AGHDA) at baseline and early (6-13 months) and long-term (24-77 months) treatment follow-up. Of secondary interest were six PGWB domains. Linear mixed effect regression was used to model each QOL outcome. The groups differed with respect to three covariates: age, gender, and body mass index. These variables were included in all fitted models. Baseline scores for PGWB and AGHDA were not different between groups. Ranking of PGWB domains were similar between groups at baseline (lowest domain, vitality). The pattern of change in mean scores for all outcome measures from baseline did not differ between groups (P = 0.86). All QOL variables improved significantly with treatment [estimated mean change +/- se: PGWB, 16.2 +/- 1.7; AGHDA, -6.2 +/- 0.6; PGWB domains (transformed percentage scales): anxiety, 12.4 +/- 1.7; depression, 14.1 +/- 2.1; health, 12.4 +/- 1.7; self-control, 11.3 +/- 2.0; well-being, 15.2 +/- 1.7; vitality, 22.5 +/- 2.0 (vitality, greatest change)]. There was no evidence of group difference in early follow-up or long-term follow-up means for any outcome variable. The QOL in adult GHD cancer survivors was comparable to that in GHD adults with pituitary pathologies and improved with GH replacement in a similar manner. We conclude that QOL impairment in adult GHD cancer survivors appears mainly related to GHD rather than cancer diagnosis and treatment.

Testicular function after cytotoxic chemotherapy: evidence of Leydig cell insufficiency.

PURPOSE: To evaluate testicular function in men after treatment with cytotoxic chemotherapy. PATIENTS AND METHODS: We measured testosterone, sex hormone-binding globulin (SHBG), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels in 209 men after treatment with mechlorethamine, vinblastine, procarbazine, and prednisone, hybrid chemotherapy, or high-dose chemotherapy and in 54 healthy age-matched controls. RESULTS: The mean age of the patients was 38 years (range, 19 to 68 years), and all patients had received chemotherapy between 1 and 22 years previously. Patients had significantly higher mean LH (7.9 v 4.1 IU/L; P < .0001) and FSH levels (18.8 v 3.1 IU/L; P < .0001) than controls. There was no significant difference in mean total testosterone level between the patients and controls, but there was a trend toward a lower mean testosterone/SHBG ratio in the patients (0.63 v 0.7; P = .08). Analysis of the hormonal parameters using a model that allowed for the effects of increasing age on testicular function showed evidence of significant recovery of gonadal function in the first 10 years after treatment. Fifty-two percent of patients had LH levels at or above the upper limit of normal, and 32% of patients had increased LH with testosterone levels in the lower half of the normal range, suggesting a degree of Leydig cell impairment. CONCLUSION: In a significant proportion of men, there is good evidence of Leydig cell dysfunction after cytotoxic chemotherapy. The clinical significance of this Leydig cell dysfunction is not clear, but some of these men may benefit from testosterone replacement. Further studies are warranted.

Gonadal function following chemotherapy for Hodgkin's disease: a comparative study of MVPP and a seven-drug hybrid regimen.

PURPOSE AND METHODS: Gonadal function was assessed in 89 patients after chemotherapy for Hodgkin's disease (HD). Thirty-seven patients had received mechlorethamine, vinblastine, prednisolone, and procarbazine (MVPP) and 52 patients, a hybrid combination of chlorambucil, vinblastine, prednisolone, procarbazine, doxorubicin, vincristine, and etoposide (ChIVPP/EVA). Fifty men (MVPP, n = 21; ChIVPP/EVA, n = 29) with a median age of 26 years (range, 16 to 54) and 39 women (MVPP, n = 16; ChIVPP/EVA, n = 23) with a median age of 30 years (range, 15 to 47) were studied at a median of 30 months (range, 4 to 83) following chemotherapy. RESULTS: Semen analysis showed azoospermia in 35 of 37 men, and increased serum follicle-stimulating hormone (FSH) levels in this group confirmed severe germinal epithelial damage. Analysis of pretreatment semen in 28 men showed azoospermia in one, oligospermia in four (sperm count < 20 x 10(6)/mL), and a normal sperm count in the remaining 23. In the women, 26 of 34 (76%) with a regular menstrual cycle before commencing chemotherapy became amenorrheic following treatment. Menses returned in 10 women, who had a median age of 25 years (range, 21 to 34), and there were two pregnancies in this group. In the other 16, with a median age of 36 years (range, 27 to 47), amenorrhea persisted and premature ovarian failure was confirmed by increased serum gonadotrophins and reduced estradiol (E2) concentrations. Of the original eight women in whom menses were maintained following treatment, two subsequently developed amenorrhea and the clinical and biochemical features of an early menopause. In total, 18 of 34 women (53%) required hormone replacement therapy for chemotherapy-induced ovarian failure. CONCLUSION: There was no statistically significant difference in the frequency or severity of gonadal dysfunction between MVPP- and ChIVPP/EVA-treated patients. We conclude that both of these chemotherapy schedules cause substantial damage to gonadal function in both sexes.

Pubertal growth in young adult survivors of childhood leukemia.

PURPOSE: To determine the effect of cranial irradiation (18 Gy and 24 Gy) on pubertal growth in young adult survivors of childhood acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: Final height (FH) and pubertal growth were retrospectively examined in 142 young adult survivors of childhood ALL. All were in first remission and had received either 18 or 24 Gy of cranial irradiation. Eighty-four children (48 girls) were treated with 24 Gy and 58 (35 girls) with 18 Gy. None had received either testicular or spinal irradiation. Timing and duration of puberty were studied in 110 patients. RESULTS: Significant reduction in height standard deviation score (SDS) from diagnosis to FH was seen in both sexes and in both dose groups. In girls, in both dose groups, mean age at peak height velocity (PHV) and mean age at menarche occurred significantly earlier than in the normal population. In boys, there was a normal timing of PHV. The amplitude of PHV was significantly reduced in both sexes and in both dose groups. Parameters of pubertal duration (PHV to menarche, PHV to FH, and menarche to FH) were not significantly different from normal population values. CONCLUSION: In conclusion, puberty occurred early in girls, but not in boys. Amplitude of PHV was reduced in both sexes, with no reduction in the duration of puberty. It is likely that disturbances of both timing and quality of growth during puberty contribute to the loss of standing height and body disproportion seen in these children.

Spermatogenesis after cancer treatment: damage and recovery.

Treatment with cytotoxic chemotherapy and radiotherapy is associated with significant gonadal damage in men, and alkylating agents are the most common agents implicated. The vast majority of men receiving procarbazine-containing regimens for the treatment of lymphomas are rendered permanently infertile, whereas treatment with doxorubicin hydrochloride (Adriamycin), bleomycin, vinblastine, and dacarbazine appears to have a significant advantage, with a return to normal fertility in the vast majority of patients. Cisplatin-based chemotherapy for testicular cancer results in temporary azoospermia in most men, with a recovery of spermatogenesis in about 50% of the patients after 2 years and 80% after 5 years. The germinal epithelium is very sensitive to radiation-induced damage, with changes to spermatogonia following as little as 0.2 Gy. Testicular doses of less than 0.2 Gy had no significant effect on FSH levels or sperm counts, whereas doses between 0.2 and 0.7 Gy caused a transient dose-dependent increase in FSH and reduction in sperm concentration, with a return to normal values within 12-24 months. No radiation dose threshold has been defined above which permanent azoospermia is inevitable; however, doses of 1.2 Gy and above are likely to be associated with a reduced risk of recovery of spermatogenesis; the time to recovery, if it is to occur, is also likely to be dose dependent.

Consensus statement on the management of the GH-treated adolescent in the transition to adult care.

The European Society for Paediatric Endocrinology held a consensus workshop in Manchester, UK in December 2003 to discuss issues relating to the care of GH-treated patients in the transition from paediatric to adult life. Clinicians experienced in the care of paediatric and adult patients on GH treatment, from a wide range of countries, as well as medical representatives from the pharmaceutical manufacturers of GH participated.

Management of constitutional delay in growt and puberty.

Constitutional delay in growth and puberty is a variant of normal growth and development that can cause a significant degree of psychological disturbance in otherwise healthy children, and is most often seen in boys of pubertal age. Careful assessment is necessary to rule out other endocrine or nonendocrine diseases. In some patients, therapy with oxandrolone or testosterone may be necessary to advance growth and/or pubertal development and thereby prevent serious psychological disturbance that can persist even into adult life. In the majority, however, reassurance will usually suffice.

Growth Hormone therapy for adult Growth Hormone deficiency.

GH deficiency in adult life is associated with a number of adverse biological changes including osteopenia, reduced exercise capacity, altered body composition, deleterious alterations in the lipid profile and insulin status, and reduced quality of life. Potentially, most of these changes can be reversed by GH replacement therapy. In an era of health rationing, however, GH replacement is unlikely to be offered to every GH-deficient adult. Therefore, we have proposed a strategy aimed at delineating which adults with GH deficiency might benefit most from GH therapy.

Thyroid hormones regulate hypertrophic chondrocyte differentiation and expression of parathyroid hormone-related peptide and its receptor during endochondral bone formation.

Hypothyroidism in children causes developmental abnormalities in bone and growth arrest, while thyrotoxicosis accelerates growth rate and advances bone age. To determine the effects of thyroid hormones on endochondral bone formation, we examined epiphyseal growth plates in control, hypothyroid, thyrotoxic, and hypothyroid-thyroxine (hypo-T4)-treated rats. Hypothyroid growth plates were grossly disorganized, contained an abnormal matrix rich in heparan sulfate, and hypertrophic chondrocyte differentiation failed to progress. These effects correlated with the absence of collagen X expression and increased parathyroid hormone-related protein (PTHrP) messenger RNA (mRNA) expression. In thyrotoxic growth plates, histology essentially was normal but PTHrP receptor (PTHrP-R) mRNA was undetectable. PTHrP is a potent inhibitor of hypertrophic chondrocyte differentiation that acts in a negative feedback loop with the secreted factor Indian hedgehog (Ihh) to regulate endochondral bone formation. Thyroid hormone receptor alpha1(TRalpha1), TRalpha2, and TRbeta1 proteins were localized to reserve zone progenitor cells and proliferating chondrocytes in euthyroid rat cartilage; regions in which PTHrP and PTHrP-R expression were affected by thyroid status. Thus, dysregulated Ihh/PTHrP feedback loop activity may be a key mechanism that underlies growth disorders in childhood thyroid disease.

The impact of cancer therapy on the endocrine system in survivors of childhood brain tumours.

Survival rates are improving following cancer therapy for childhood brain tumours. There is therefore a growing cohort of survivors at risk of late effects of cancer therapy. Endocrine problems are very common in these patients. The recognition and prompt management of these are essential to prevent further morbidity and impairment of quality of life. Cranial radiation can damage hypothalamic-pituitary function, most frequently affecting GH status; however, higher radiation doses may cause more widespread hypothalamic-pituitary damage. Early puberty secondary to cranial irradiation is now being managed with gonadotrophin-releasing hormone analogues to improve final height. Prompt diagnosis and management of GH deficiency may improve final height outcome; continued GH therapy beyond final height aids the achievement of adult body composition (lean body mass and bone mass) and GH therapy in adulthood improves quality of life. Both cranial irradiation alone and with spinal irradiation can result in radiation damage to the thyroid resulting in hypothyroidism and thyroid nodules, a high proportion of which are malignant. Gonadal damage secondary to spinal irradiation and adjuvant chemotherapy may have long-term consequences including infertility.

Thyroid hormone acts directly on growth plate chondrocytes to promote hypertrophic differentiation and inhibit clonal expansion and cell proliferation.

T3 is an important regulator of endochondral bone formation in epiphyseal growth plates. Growth arrest in juvenile hypothyroidism results from disorganization of growth plate chondrocytes and their failure to undergo hypertrophic differentiation, but it is unclear how T3 acts directly on chondrocytes or whether its actions involve other pathways. To address this issue, we investigated whether thyroid hormone receptors (TR) were localized to discrete regions of the unfused epiphysis by immunohistochemistry performed in tibial growth plates from 21-day-old rats and examined the effects of T3 on growth plate chondrocytes in agarose suspension cultures in vitro. TRalpha1, -alpha2, and -beta1 were expressed in reserve and proliferating zone chondrocytes, but not in hypertrophic cells, suggesting that progenitor cells and immature chondrocytes are the major T3 target cells in the growth plate. Chondrocytes in suspension culture expressed TRalpha1, -alpha2, and -beta1 messenger RNAs and matured by an ordered process of clonal expansion, colony formation, and terminal hypertrophic differentiation. Clonal expansion and proliferation of chondrocytes were inhibited by T3, which also induced alkaline phosphatase activity, expression of collagen X messenger RNA, and secretion of an alcian blue-positive matrix as early as 7 days after hormone stimulation. Thus, T3 inhibited chondrocyte clonal expansion and cell proliferation while simultaneously promoting hypertrophic chondrocyte differentiation. These data indicate that thyroid hormones concurrently and reciprocally regulate chondrocyte cell growth and differentiation in the endochondral growth plate.

Growth hormone replacement therapy in the elderly with hypothalamic-pituitary disease: a dose-finding study.

Adults over the age of 60 yr with organic disease of the hypothalamic-pituitary axis have a 90% reduction in GH secretion. This is distinct from the hyposomatotropism associated with increasing age and results in a significant reduction in serum insulin-like growth factor I (IGF-I), an increase in fat mass, abnormal bone turnover, and an adverse lipid profile compared with those in healthy subjects of the same age. These findings suggest that the elderly with organic GH deficiency might benefit from GH replacement therapy. However, the dose of GH required to maintain serum IGF-I levels in the normal range while minimizing side-effects in this group of patients is unknown. We have studied 12 patients with organic GH deficiency, aged 62.4-85.2 (median, 67.9 yr), each treated with three doses of GH (0.167, 0.33, and 0.5 mg/day). Each dose was administered for 12 weeks. The serum IGF-I level rose in a dose-related manner over the course of the study (P < 0.0001). From a baseline median (range) IGF-I concentration of 101 (49-148) microg/L to 149 (49-227) microg/L at 12 weeks (P = 0.003 vs. baseline), 200 (70-453) microg/L at 24 weeks (P = 0.002 vs. baseline; P = 0.04 vs. 12 weeks), and 239 (122-502) microg/L at 36 weeks (P = 0.002 vs. baseline; P = 0.07 vs. 24 weeks). The age-specific IGF-I SD score exceeded normal in two subjects taking 0.33 mg/day and in six subjects taking 0.5 mg/day. Serum IGF-binding protein-3 also rose over the course of the study (P < 0.001); however, the greatest increase occurred during the first 12 weeks, after which the IGFBP-3 level plateaued. Body composition changed significantly during the study, with a fall in fat mass (P = 0.0003) and an increase in lean body mass (P = 0.0001). GH was well tolerated in this elderly group, all of whom completed the study. Three patients developed side-effects while taking 0.5 mg/day; two developed headaches, and one developed arthralgia. This study has demonstrated that the GH replacement dose in elderly subjects is considerably lower than that required by younger adults with GH deficiency. In 50% of the subjects a dose of 0.5 mg/day was excessive, whereas 83% maintained their serum IGF-I within normal limits while taking 0.33 mg/day. No patient exhibited a supranormal IGF-I level on 0.17 mg/day.