Effect of Estrogen Therapy on Carbohydrate Metabolism in Acromegaly

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Abstract
The effects of high-dose estrogen therapy upon carbohydrate and insulin metabolism in 4 female acromegalic patients were evaluated. The effects of treatment with estrogen on oral glucose disposal rates were different between patients and in each patient varied with either the dose, duration, or nature of the estrogen. A reduction in the concentration of the fasting blood glucose or an improvement in oral glucose tolerance or both was initially observed. More prolonged estrogen therapy reversed the initial beneficial effects. Estrogen therapy inhibited the augmented plasma insulin response to both glucose and arginine stimulation, increased, the plasma growth hormone response to insulin-induced hypoglycemia, and appeared to increase the sensitivity to endogenous insulin. During estrogen therapy, the concentration of fasting plasma growth hormone was consistently and significantly reduced in only one of the patients. These observations indicate that the initial effects of estrogen therapy upon carbohydrate and insulin metabolism in patients with acromegaly are due to an antagonism to the anti-insulin and islet cell stimulatory actions of growth hormone. Whether this antagonism is due to a direct cellular inhibition of growth hormone or is mediated through some other pituitary or extrapituitary effect of estrogens are possibilities that remain to be evaluated.