Studies of the Sex Based Variation of Human Growth Hormone Secretion

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Abstract
A comprehensive study was undertaken to clarify the nature of a sex-based variation of human growth hormone (HGH) secretion in man. This included a detailed investigation of HGH secretion after several stimuli in both sexes and in females during the menstrual cycle. Pretreatment with appropriate sex hormones was carried out. Graded doses of arginine were infused in each period of the menstrual cycle. During a high estrogen phase of the cycle (preovulatory phase) the mean peak human growth hormone response to 1/6 g and to 1/12 g of arginine per pound of body weight was significantly greater than during menstruation—a low estrogen phase. A similar variation did not occur with a greater dose (1/4 g per pound of body weight) of arginine. Graded decreases of plasma glucose induced by insulin revealed a similar pattern. With plasma glucose concentration decreasing between 20 and 30 mg/100 ml, HGH increased in the preovulatory phase to 17.5 ± 5.0 mμg/ml, in the postovulatory phase to 14.0 ± 4.2 mμg/ml, and during menstruation to only 6.9 ± 2.2 mμg/ml. When decreases of plasma glucose exceeded 40 mg/100 ml, the HGH response was quantitatively similar in each phase of the menstrual cycle. Males responded to graded decreases of plasma glucose in a manner quantitatively similar to menstruating females. The growth hormone response of males to arginine was significantly augmented by pretreatment with estrogen (18 paired studies). Testosterone and methyltestosterone (27 paired studies) had no effect on the HGH response of males. The increase of plasma glucose concentration after arginine was less following diethylstilbesterol treatment of males. In females it was consistently less in high estrogen phases of the menstrual cycle. Plasma insulin responses to arginine were quantitatively similar in all studies. Overall, the data are consistent with a homeostatic interplay between estrogen and growth hormone.

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