AGING ALTERS FEEDFORWARD AND FEEDBACK LINKAGES BETWEEN LH AND TESTOSTERONE IN HEALTHY-MEN

To discern the effect of aging on coordinate luteinizing hormone (LH) and testosterone secretion, we sampled healthy older men (age 62-74 yr , n = 11) and young controls (age 21-34 yr, n = 13) every 2.5 min over night. Deconvolution analysis and cross-correlation were used to relat e serum LH concentrations to calculated testosterone secretion rates ( feed-forward stimulation), as well as serum testosterone concentration s to computed LH secretion rates (feedback inhibition). Despite statis tically similar mean serum LH and testosterone concentrations in the y oung and older men, older individuals had diminished feed-forward stim ulation of LH concentrations on calculated testosterone secretion rate s, as well as delayed feedback inhibition of testosterone concentratio ns on computed LH secretion rates.