Search

To elucidate the effect of somatostatin on basal, unstimulated TSH secretion 6 young healthy nonobese men were studied with blood samples every 15 min from 2300 h to 0500 h. Somatostatin 1 mg was indused over a 2-h period from 0100 h. One of the subjects was also studied with half hourly blood samples throughout a 26-h period without receiving somatostatin. In all cases the high night levels of serum thyrotropin (TSH) were significantly suppressed by somatostatin. The fall of TSH continued throughout the two hour infusion period. Immediately upon termination of the infusion serum TSH increased rapidly to preinfusion values. The 26-h control study showed the typical diurnal pattern of serum TSH with low values in the daytime and high values at night. The serum triiodothyronine (T3) and thyroxine (T4) levels were not changed by somatostatin infusion. From these results we suggest that endogenous somatostatin may be of physiological importance in the regulation of the TSH secretion.

Somatostatin 5, 10, and 25 mug and saline were given as a 2 min bolus injection to 6 acromegalic patients in basal conditions. A significant dose-response relationship could be demonstrated between somatostatin and the suppressions of plasma growth hormone and insulin. The lowest somatostatin dose tested exerted a significant suppression of both hormones. Insulin suppression after the bolus injection lasted for 15 minutes, while the suppression of growth hormone was maintained for 30-50 minutes. In order to obtain total suppression of the elevated plasma growth hormone levels in acromegalics, 3 patients received 50, 250, and 500 mug of somatostatin as bolus injections at time 0, 90, and 180 minutes, 2 patients received 50 mug of somatostatin as bolus injections 4 times with an interval of 20 minutes between each injection, and finally 3 patients received a large dose of somatostatin, 3000 mug given as an infusion over 2 hours. The single injections of somatostatin were not followed by a satisfactory growth hormone suppression. In the infusion experiments, the average plasma growth hormone level was suppressed only 65%, resulting in individual plasma growth hormone plateaus of 20, 14, and 3.6 ng/ml. Only the lowest of these plateaus would be acceptable from a clinical point of view.