Effect of Sex and Age on Serum Aldosterone and Thyroid Hormones in the Laboratory Rat

Abstract

Serum levels of aldosterone, tri-iodo thyronine (T₃) and thyroxine (T₄) were measured in male and female rats aged 3 months, 12 months, and 18 months. Female rats were found to have higher aldosterone and T₃ levels, and lower T₄ level than the male. No age-related change was observed in serum aldosterone in either sex. In contrast, serum T₄ were found to decrease with age in both sexes while serum T₃ showed an age-associated diminution in the male only. Serum testosterone was also measured in the male rats and was found to decline with age.