1981 Volume 18 Issue 6 Pages 403-409
Effect of advancing age on the pituitary function has been uncertained. In the present paper, in order to evaluate the role of aging in pituitary responses following thyrotropin-releasing hormone (TRH) injection, 11 carefully selected healthy subjects (5 males and 6 females) over eighty years, in comparison with 40 young healthy controls (20 males and 20 females), ranged from 21 to 35 years, were examined. Thyroxine (T4) and triiodothyronine (T3) concentration in the serum and T3-uptake (Thyrotest-3) value were determined and the serum thyrotropin (TSH), prolactin (PRL) and growth hormone (GH) responses to TRH were evalulated. There were no differences in the serum T4 concentration, the value of Thyrotest-3, free thyroxine index (FTI) and the serum basal PRL and GH concentration between elderly subjects and young controls, on the other hand, the serum T3 and basal TSH concentration were slightly lower, but not statisticaly significant, in elderly subjects than in young controls. When compared with the young controls, the serum TSH response to TRH was definitely reduced or even abscent in 5 elderly subjects and the serum TSH decrease after the maximum value following TRH injection was delayed in 4 elderly subjects. In 2 of 5 elderly subjects in whom TSH response to TRH was reduced or even abscent, the serum PRL response to TRH was definitely reduced as compared with the young controls. In only one of 11 elderly subjects TRH raised significantly the serum GH level (the peak level, 8.0ng/ml).
These findings may suggest a decreased sensitivity of the pituitary TRH receptor to TRH with aging and the possibility of changes with aging in hypothalamic catecholamine contents.
