Effect of advancing age on thyroid hormone secretion rate of male and female rats.

Abstract

SummaryThe thyroid hormone secretion rate (TSR) of the same group of 36 male rats was estimated at 30 days and at 30-day intervals to 120 days. They declined from a mean of 1.40 μg/100 g bw to 1.03 μg at 120 days or 26%. A group of 118 male rats at 30 days of age had a mean TSR of 1.34 μg 100 g bw with a range from 0.75 μg to 2 μg /100 g bw. The TSR of a group of 29 females at 30 days of age was 1.47 μg/100 g bw and gradually declined to 0.87 μg at 240 days of age or 41%. It was shown that the TSR of both male and female rats decline with age but the rate of decline may vary in different groups of animals.