Changes of hormonal function of the adrenal and gonadal glands in baboons of different age groups.

The purpose of this study was to characterize the changes of hormonal function of the adrenals and gonads during aging in male baboons (Papio hamadryas). Basal levels of plasma dehydroepiandrosterone, dehydroepiandrosterone sulfate, pregnenolone, and 17-hydroxypregnenolone progressively decrease with age from 10-15 years when analyzed by specific radioimmunoassay. However, no significant changes were found in cortisol and 11-desoxycortisol concentrations. The levels of sexual hormones did not differ in young and mature groups. In the 20-26-year-old animals, the concentration of testicular androgens showed a tendency to decrease, while the concentration of biologically active luteinizing hormone (LH) showed a tendency to increase. The old animals exhibited a decrease of plasticity of the pituitary testicular system, which was manifested in the deceleration of the decrease of LH and T concentrations after the peak values had been reached in response to luteinizing hormone-releasing hormone (LHRH) administration. The oldest male also developed some refractoriness of the pituitary gonadal system to the prolonged administration of LHRH agonist. The hormonal imbalance which develops with age may play an important role in the age-related involutional process.