EFFECTS OF THYROID-HORMONE STATUS ON THE GROWTH-HORMONE RESPONSES TO CLONIDINE

It has been shown that thyroid hormones are positive regulators of GH synthesis and secretion. The serum GH response to stimuli seems to be influenced either by sex or by spontaneous hypothalamic rhythm. The gr owth hormone responses to clonidine administration (4 mug/kg) have bee n therefore studied in a group of female patients with thyroid disease (seven hyperthyroid and five hypothyroid) before and after the achiev ement of the euthyroid state. In hyperthyroid patients both basal and clonidine-stimulated GH levels were similar to normal subjects; the ac hievement of euthyroidism did not modify the GH response to clonidine. Serum GH peaks after clonidine were lower in hypothyroids patients th an in hyperthyroids and normal subjects; the GH response to alpha2-ago nist administration did not change during thyroid replacement therapy. The GH response to clonidine was not influenced by the GH secretory s tatus in the preceding hour.