Increase of serum GH concentration following TRH injection in patients with primary hypothyroidism

The effect of TRH administration on serum GH was studied in 6 normal subjects, 13 patients with primary hypothroidism and 6 thyrotoxic subjects. Although no appreciable changes of serum GH were noted in the normal subjects, TRH administration provoked an increase of serum GH in 6 out of 13 patients with primary hypothyroidism. Serum GH levels in response to TRH administration were decreased in patients who were euthyroid following treatment with a preparation of desiccated thyroid. In patients with hyperthroidism, no significant response of serum GH was observed at 30 or 60 min after TRH administration. Some of the patients with hyperthyroidism showed a slight increase in serum GH at 120 min after TRH injection. These results suggest that hypothalamo-pituitary function regulating GH secretion is altered in patients with primary hypothyroidism.