Sleep-related growth hormone release in thyrotoxic patients before and during propylthiouracil therapy

Hyporesponsiveness of GH to insulin-induced hypoglycemia has previously been reported in hyperthyroid patients. In order to clarify the GH secretion in thyrotoxic patients, sleep-related increases in the serum GH concentration were investigated. Eight thyrotoxic females ranging in age from 7 to 15 were treated with PTU. Blood samples for measurement of GH were drawn every 15 minutes during the first few hours of sleep before and during the treatment lasting about three months. The mean maximum serum GH level before the treatment was 10.0 +/- 5.5 ng/ml (mean +/- SD); this rose to 23.2 +/- 14.6 ng/ml (P less than 0.02) during the treatment. The maximum value of more than 10 ng/ml was detected in only 3 out of the 8 patients before treatment. On the other hand, serum GH levels during PTU administration rose to above 10 ng/ml in all patients except one. It was revealed that sleep-related elevations of GH occurred early in sleep and in close association with a slow-wave EEG pattern. The results show that sleep-related GH release is low in the hyperthyroid state, but becomes significantly elevated during PTU administration. However, even in the hyperthyroid state, the sleep-related secretion of GH is closely correlated with the slow-wave sleep stage as in the euthyroid condition.