Acute and chronic estrogen effects upon serum somatomedin activity, growth hormone, and prolactin in man.

ABSTRACT

PIP: Acute and chronic estrogen effects upon serum somatomedin (SM) activity, growth hormone (GH), and prolactin were studied in adult male subjects. Administration of .5 mg ethinyl estradiol/day for 7-70 days reduced serum SM activity by 40-62% in each of 4 subjects (p less than .02 to less than .001). In 3 subjects, basal GH levels increased 75-300% (P less than .05 to less than .001) and basal prolactin levels increased by 90-200% (p less than .01 to less than .001). Intravenous (iv) administration of saline did not markedly affect SM or GH while the iv administration of 25 mg conjegated estrogens to 5 subjects resulted in: 1) a 46-80% decrease in serum SM activity in all subjects proceeding with an apparent 1/2-life of 2 hours, becoming significant (p .05) at 2-3 hours and persisting for 12-24 hours, 2) GH elevation to 3-16 times baseline level (p .01) at 2-3 hours and 3) no marked change in prolactin levels. These results indicate that in males with normal pituitary function, estradiol reduces serum SM activity, enhances basal GH and prolactin secretion and, upon iv injection, stimulates acute GH release. It is suggested that the 1/2-life of serum SM activity in the human is probably much shorter than previously estimated.