Effect of estrogen on the growth hormone response to the alpha-adrenergic agonist clonidine in women with menopausal flushing.

The serum GH response to the alpha 2-adrenergic receptor agonist clonidine (0.15 mg, iv) was measured in 8 postmenopausal women with hot flushes before and during treatment with the conjugated estrogen premarin (1.25 mg, orally daily for 4 weeks), 9 normal premenopausal women, and 12 normal men. The men had a significantly greater GH response than did the age-matched premenopausal women (P less than 0.05). The mean individual peak GH response was significantly higher in the premenopausal compared with the postmenopausal women (P less than 0.05). Premarin decreased the number of hot flushes (P less than 0.01), but had no effect on the GH response to clonidine. These results suggest that estrogens do not enhance alpha 2-adrenergic mechanisms that regulate GH secretion and that improvement in menopausal flushing after estrogen therapy is not mediated by an effect on central alpha 2-adrenergic function.