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1 Medical Service, Wm. Jennings
Bryan Dorn Veterans' Hospital and
Department of Medicine, University of
South Carolina School of Medicine,
Columbia, South Carolina
To assess the capacity of aging human Leydig
cells to respond to intramuscular injection of
hCG, six healthy men, 68 to 86 years old, and
eight healthy younger subjects, 25 to 42 years
old, were studied. After two control specimens,
each subject was given hCG (40 IU/kg of body
weight intramuscularly) at 0900 hours. Blood
specimens were then obtained hourly for 6
hours and at 24, 48, and 72 hours. The younger men had higher control concentrations of testosterone (P < 0.05). Both
groups demonstrated biphasic elevations of
circulating testosterone and 17OH-progesterone with a nadir at 5 hours and 6 hours separating the rises. The early (1-6 hours) and late
(24, 48, and 72 hours) testosterone and 17OH-progesterone responses to hCG were significantly lower in older men. The older men demonstrated significant estradiol increases at 3,
4, and 6 hours, while the younger group had a
significant 2-hour rise. However, the peak (24-hour) estradiol rises were significantly greater
in the younger men. We conclude that the aged Leydig cell demonstrates altered early (1-6 hours) and late (24,
48, and 72 hours) responses to intramuscular
injection of hCG, as assessed by circulating
concentrations of testosterone, 17OH-progesterone, and estradiol.
Key words: human, aging, Leydig cells, testosterone, 17OH-progesterone, estradiol, human chorionic gonadotropin
Submitted on December 1, 1980
Revised on January 21, 1981
Accepted on February 3, 1981
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