Reproductive hormones in aging men. III: Basal and LHRH-stimulated serum concentrations of the common alpha-subunit of the glycoprotein hormones.

In a previous study, we described unaltered basal serum levels of sex steroids, increased basal luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and diminished and/or delayed gonadotropin responses to exogenous luteinizing hormone releasing hormone (LHRH) in 69 healthy men, aged 25 to 89 years, in the Baltimore Longitudinal Study of Aging. Here we report basal and LHRH-stimulated serum concentrations of the common alpha-subunit of the glycoprotein hormones in 53 of these same men, divided into groups: A, 25 to 49 years, (n = 22); B, 50 to 69 years, (n = 18); and C, 70 to 89 years, (n = 13). There were no significant (p greater than .2) age-related alterations in basal serum concentrations of the alpha-subunit. Using repeated measures analysis of variance (ANOVA), we found a significant difference between basal levels and peak responses to LHRH for alpha-subunit in each group (p less than .001); however, age per se did not influence the magnitude of this response (p greater than .1). Frequency distribution analysis of the time of the peak alpha-subunit response across age groups demonstrated a significant age-related delay in the timing of the peak alpha response (p less than .03). These data, in conjunction with our prior observations, suggest that in healthy men there may be age-related alterations in the secretion and/or metabolic clearance of pituitary gonadotropins and their component subunits.