[Immunoelectron microscopic study of growth hormone cells in hyper- and hypothyroid rats].

Male Sprague Dawley rats were rendered hyperthyroid and hypothyroid by the intraperitoneal injections of 1-thyroxine or methimazole and sacrificed 21 days after the start of the treatment. The pituitaries were studied by immunoelectron microscopy by the immunogold labeling technique. In both hyperthyroidism and hypothyroidism, the numbers of growth hormone (GH) cells, GH-secreting granules and immunogolds in the secretory granules all were significantly decreased as compared with those in controls. The results indicate that low or high levels of thyroid hormones may cause decrease of GH production of the pituitary.

[Clinical significance of thyrotropin measurement by immunoradiometric assay and thyrotropin-releasing hormone test].

The levels of serum TSH were measured by a sensitive immunoradiometric assay (IRMA) method and the responses of TSH to TRH stimulation were observed in three groups of hyperthyroidism, primary hypothyroidism and secondary hypothyroidism. The levels of serum TSH were found to be undetected in 98% (1/51) of the patients with hyperthyroidism, very high in 100% (35/35) of the patients with primary hypothyroidism and normal in 91% (30/33) of the patients with secondary hypothyroidism. TRH test showed no responses of TSH in all patients with hyperthyroidism, high responses in all patients with primary hypothyroidism and blunt responses in 69% (11/16) of patients with secondary hypothyroidism. The results indicate that the measurement of serum TSH by IRMA is a sensitive index in the diagnosis of hyperthyroidism and primary hypothyroidism, but can not be differentiated the secondary hypothyroidism from normal conditions. TRH test may be helpful in the differential diagnosis between secondary hypothyroidism and normal conditions.

Effects of aminoglutethimide on hypothalamic-pituitary-adrenal functions.

This study was performed on four groups of subjects, including 10 patients with Cushing's disease, 10 patients with simple obesity, 8 patients with hypopituitarism and 13 normal subjects. The study was conducted by measuring the sequential changes of plasma ACTH, serum cortisol, 24-h UFC, 24-h 17 KS and 24-h 17 KGS following aminoglutethimide (AG) administration. The results suggest that normal subjects showed sequential changes of hypothalamic-pituitary-adrenal hormone concentrations with normal feedback regulation of the axis following AG administration. Patients with Cushing's disease had obvious autonomy in the production of ACTH from the pituitary. Patients with simple obesity might display abnormality to some degree in the production from the pituitary. Patients with hypopituitarism lost the capacity of ACTH production in various degrees because of pituitary lesions.

Non-specific response of serum growth hormone to thyrotropin-releasing hormone in diabetics.

It is well known that growth hormone (GE) secretion and regulation in diabetics are abnormal. In order to evaluate the response of GH to nonphysiological stimuli in diabetics, a thyrotropin-releasing hormone (TRH) test (500 micrograms by IV bolus injection) was carried out in 12 patients with insulin-dependent diabetes (IDD, 6 males and 6 females). 11 noninsulin-dependent diabetes (NIDD, 5 males and 6 females), and 10 normal controls (6 males and 4 females). The results showed that the basal serum GH levels in diabetics were higher than that in normal controls and it was even higher in IDD than in NIDD. Following the TRH stimulus, the mean peak level of GH in IDD was the highest among the three groups, the differences being statistically significant (F = 9.323, P less than 0.01). It was concluded that a nonspecific response to TRH of GH did occur in IDD, and the peak values were even higher in female than in male subjects. A negative correlation existed between the GH peak values and the age of the patients as well as in the controls. This supported the view that GH responsiveness to TRH has a tendency of progressive decline with age. However, no significant correlation was found between the peak value of GH and the blood glucose level or the microangiopathic complications. The mechanism of TRH stimulation on GH release in diabetics is discussed.