The effect of hGH on hypothalamic-pituitary-thyroid function in patients with pituitary dwarfism

The effect of growth hormone (hGH) on the hypothalamic-pituitary-thyroid function was studied in patients with pituitary dwarfism. Twenty-six patients were given KABI hGH, 0.5 U/kg/week, for a period of 4—18 months. Three groups of patients were identified according to their T4 levels before and during the treatment. Group 1: T4 levels were initially normal and stayed in the normal range throughout a course of treatment. Group 2: T4 levels were initially normal but dropped to the subnormal range after hGH. Group 3: T4 levels were initially subnormal and decreased further after hGH. Changes in T4 levels after hGH in groups 2 and 3 were accompanied by a decrease in plasma T3RSU without concomitant decrease in plasma T3. Clinically, most of them lacked symptoms and signs of hypothyroidism and exhibited a good growth response to hGH. Plasma TSH response to TRH in these patients revealed a sustained delayed pattern, which was suggestive of hypothalamic hypothyroidism. This pattern of TSH response to TRH became further exaggerated after hGH therapy. In contrast, TSH response to TRH among patients in group 1 was normal and was not influenced by hGH. Administration of 4.0 U of KABI hGH daily for 21 consecutive days to 3 patients resulted in a shortened half-life of T4 and inversely prolonged that of T3.

These results suggest that various degrees of TRH deficiency exist among patients with idiopathic pituitary dwarfism. Therapy with hGH discloses a mild TRH deficiency by accelerating the half-life of T4. This also causes a further drop in the T4 levels in those with marked TRH deficiency. The development of clinical hypothyroidism is not so obvious in these patients because of inverse delay in half-life of T3 by hGH.

Chlorpromazine inhibits episodic growth hormone secretion in the rat

Effects of chlorpromazine (CPZ) on plasma GH and prolactin levels were observed in conscious rats provided with chronic indwelling right atrial cannulae. The administration of CPZ (200 micrograms/100 g b.w. iv) suppressed episodic plasma GH burst and resulted in significant elevations of plasma prolactin levels. These were also observed in rats in which two types of hypothalamic deafferentation, i.e. anterior and complete, had been carried out. The data suggest that CPZ acts within the medial basal hypothalamus and inhibits episodic plasma GH secretion. In addition, it is inferred that catecholamines are involved in the generation of episodic plasma GH burst.

A case of histiocytosis X associated with panhypopituitarism and hyperimmunoglobulinemia G and E

A 43 year old man with diabetes insipidus who showed panhypopituitarism and marked hypergammaglobulinemia due to histiocytosis X is reported. His low basal plasma adrenocorticotropin (ACTH) and growth hormone (GH) failed to respond to insulin-induced hypoglycemia. His basal serum thyroid hormone level was below normal and normal basal plasma thyrotropin (TSH) showed a delayed response with normal peak value to TSH-releasing hormone (TRH). Normal basal plasma pituitary gonadotropin also showed a delayed response with normal peak value to luteinizing hormone-releasing hormone (LH-RH). Suppression of plasma prolactin (PRL) by levodopa (l-dopa) was impaired and elevation of basal plasma PRL was noted at the second admission. These results, combined with diabetes insipidus, suggested that the panhypopituitarism in these patients was hypothalamic in origin. The polyclonal hypergammaglobulinemia was characterized by elevated serum IgG and IgE levels which returned to normal after corticosteroid treatment with concomitant clinical improvement. Elevated serum IgE levels, tissue and peripheral eosinophilia, and the effectiveness of corticosteroid therapy support the hypothesis that some allergic mechanism may be involved in the pathogenesis of this disease.

Plasma TSH and prolactin response to insulin induced hypoglycemia in patients with hypothalamic pituitary disorders

Plasma TSH and prolactin (PRL) responses to insulin-induced hypoglycemia (ITT) were examined in 37 patients with various hypothalamic pituitary disorders. Four patients showed a definite TSH response to ITT. They were 2 patients with suspected pinealoma with diabetes insipidus (DI), a patient with pituitary adenoma and a patient with acute prophyria. A suspected hypothalamic dysfunction and a slightly impaired pituitary function manifested as GH deficiency were their common endocrinological features. On the contrary, plasma PRL response to ITT was noted in about one third of the patients examined, but no concomitant PRL response was observed in any of the patients with a definite TSH response. This suggested a different mechanism of TSH and PRL secretion may be different under this circumstance and a certain factor related to the hypothalamic disorder may play a modulating role in an unusual TSH response to hypoglycemia in these particular patients.

Panhypopituitarism and anemia secondary to traumatic fracture of the sella turcica

A case of a 27 year old man who developed anemia after fracture of the sella turcica is reported. The diagnosis of anterior pituitary insufficiency was made by a combined provocative test with TRH, LHRH, and insulin. The anemia was characterized by a hypocellular bone marrow which appeared to be functioning only in the thoracic-lumbar vertebrae, an absence of measurable erythropoietic activity, and by the return to normal of the hematological findings after hormonal replacement therapy. This patient had the highly unusual combination of proven panhypopituitarism and significant anemia resulting from a distinct fracture of the sella turcica.

[Role of hypothalamic somatostatin in the regulation of growth hormone secretion in the rat (author's transl)]

Series of studies were performed to elucidate the role of hypothalamic somatostatin in the regulation of growth hormone (GH) release in rats. Somatostatin was determined by a specific radioimmunoassay. In the first series of experiments, the effects of hypophysectomy, thyroidectomy, the administration of hGH and thyroxine on the hypothalamic somatostatin content were examined. Among these treatments, only hypophysectomy resulted in a significant reduction in somatostatin content and none of the rest of treatments altered somatostatin content. These results suggest that somatostatin content in the hypothalamus did rarely change in response to various endocrine treatments when anatomical connections between hypothalamus and pituitary gland were intact. In the second series of experiments, the effects of dopamine, high (K+) and Ca++ on the release of somatostatin from isolated hypothalamic synaptosomes were studied. Dopamine and high (K+) in the media stimulated the release of somatostatin and the latter effect was completely abolished by the removal of Ca++ from the media. The results suggest that dopamine has a role in modulating the release of somatostatin. In the third series, the effects of hypothalamic deafferentation on plasma GH levels and responses to ether stress were examined. Somatostatin content in the hypothalamus was reduced to about 50% in both anterior (AC) and complete deafferented (CC) rats as compared to their respective controls. The mean plasma GH levels were elevated in AC rats and the levels in CC rats were significantly higher than the control. Plasma GH levels 15 min after ether stress reduced significantly in both AC and CC rats, similarly to their respective controls. These findings suggest that the major portion of hypothalamic somatostatin was provided by other regions of the brain, which did not play a role in mediating stress-induced plasma GH reductions, but appeared to be responsible for maintaining basal GH levels.

Stimulation of immunoreactive somatostatin release from hypothalamic synaptosomes by high (K+) and dopamine

Effects of high (K+) and dopamine on the release of immunoreactive somatostatin from isolated hypothalamic synaptosomes were studied in rats. High (K+) (60 mM) and dopamine (10(-6) M) in the incubation media stimulated the release of immunoreactive somatostatin and the former effect was completely abolished by the removal of Ca++ from the media. These suggest that hypothalamic somatostatinergic synaptosomes preserved at least one of the important basic properties of secretory cells. Although it is of interest to note that dopamine stimulated the release of somatostatin. Its physiological significance awaits further studies.

Corticotropin-releasing factor-like activity in ACTH producing tumors

Corticotropin-releasing factor (CRF)-like activity in two different kinds of ACTH-producing tumors (human ectopic ACTH-producing colonic cancer and rat MtT/F4 tumor) was determined by an in vitro method using isolated normal rat pituitary cells. The ACTH content of the post mortem colonic cancer was 5.5 ng/g w.wt. The ACTH content of the medium of MtT/F4 tumor cells was 153+/-32 pg/10(5) cells. The ACTH content of MtT/F4 tumor cell suspensions was elevated with increasing doses of hypothalamic median eminence extract (HME). The response of MtT/F4 tumor cells to HME was suppressed by 1 mug/ml of dexamethasone. Extracts of colonic cancer, MtT/F4 tumor and HME produced elevation of the ACTH content of the medium of isolated rat pituitary cells. The CRF-like activities of two kinds of tumor extracts in multiple dilutions ran parallel to that of HME. The CRF-like activities were 0.037 HME equiv/mg w.wt in MtT/F4 tumor and 0.052 HME equiv/mg w.wt. in colonic cancer. These results demonstrated that CRF-like activity existed in these two kinds of ACTH-producing tumors.

Effect of hypophysectomy on hypothalamic somatostatin content in rats

The effect of hypophysectomy on the hypothalamic somatostatin content was examined in rats. Somatostatin content in the acid extract of the pituitary stalk and the median eminence tissue (SME) was measured by specific radioimmunoassay. In young male rats, the mean somatostatin content in SME was 63.9+/-5.0 ng. Two weeks after hypophysectomy, it was reduced significantly to 34.4+/-3.3 ng. The result may indicate that the elimination of feedback actions of GH and/or TSH on the hypothalamus led to the decreased synthesis and/or the release of somatostatin. However, the possibility that structural changes in the pituitary stalk and the median eminence tissue ensued after hypophysectomy resulted in the depletion of somatostatin cannot be ruled out.

Isokinetic External Rotation Strength of Shoulder: Correlation with Age and Muscle Size

The purpose of this study was to determine the correlation between quantitative (cross sectional areas)evaluation of the posterior cuff muscles and mechanical strength in asymptomatic shoulders with specialreference to aging. The cross-sectional area of the combined infraspinatus and teres minor muscles weremeasured, in the sagittal oblique magnetic resonance images, in eighty-one patients with a mean age of44.06 years (range 19 - 74). These areas were correlated with the measured isokinetic strength in externalrotation at angular velocities of 60 deg/s and 180 deg/s using Cybex 770 NORM. The results show that therewas a gradual decrease in size of the muscles as the age of the individual increases. A strong correlation wasfound between aging and combined cross-sectional area and peak torque as well. The correlation betweencombined cross-sectional area and peak torques at both angular velocities were less strong. Further, thecorrelation between the peak torque/cross-sectional area ratio with aging was also less significant, whichmay imply that the decrease in the muscle strength was greater than the change in muscle area. Our resultssuggest that there may be other qualitative and biochemical factors that may determine the true strengthof the muscles in the aged population.Key Words: Aging, muscle, cross sectional area, strength, shoulder.