Sexual behaviour of male rats thyroidectomized prior to puberty and during adulthood

Abstract (1) Twenty-one day old male rats were radiothyroidectomized by 131 I exposure, and 3–4 month old male rats were surgically thyroidectomized. (2) Parameters of sexual behaviour were compared with those of intact controls of each age group. These included the number of intromissions and ejaculations, number of intromissions needed for one ejaculation, their time elapsing until the first ejaculation, and the duration of the refractory and activity periods. (3) Sexual drive increased in rats thyroidectomized at 21 days of age; however, their ejaculatory ability decreased. (4) In contrast, rats thyroidectomized at 3–4 months of age demonstrated an increase in sexual drive as well as in ejaculatory ability. (5) Previous results suggested that after a ‘critical period’, growth hormone (GH) and thyroid hormones are not necessary for testicular development. (6) The present investigation suggests that despite diminished GH and thyroid activity, sexual behaviour was not markedly altered. (7) Nevertheless, the differences observed between the thyroidectomized groups and their controls suggest that the thyroid may influence the neural mechanism responsible for sexual drive and ejaculation.