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 funct ion of the adrenals and gonads during aging in male baboons (Papio hamadrya s). Basal levels of plasma dehydroepiandrosterone, dehydroepiandrosterone s ulfate, pregnenolone, and 17-hydroxypregnenolone progressively decrease wit h age from 10-15 years when analyzed by specific radioimmunoassay. However, no significant changes were found in cortisol and 11-desoxycortisol concen trations. The levels of sexual hormones did not differ in young and mature groups. Ln the 20-26-year-old animals, the concentration of testicular andr ogens showed a tendency to decrease, while the concentration of biologicall y active luteinizing hormone (LH) showed a tendency to increase. The old an imals exhibited a decrease of plasticity of the pituitary-testicular system , which was manifested in the deceleration of the decrease of LH and T conc entrations after the peak values had been reached in response to luteinizin g hormone-releasing hormone (LHRH) administration. The oldest male also dev eloped 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.