Combined effects of neonatal thyroxine treatment and neonatal castration on sebum production in adult male rats.

Newborn Sprague-Dawley rats were castrated within 24 h of birth and control animals were sham-operated. Intact female rats were also included for comparison. One-half of the rats in each group was treated with 28 micrograms thyroxine (t4) daily for the first week of life. The secretion rate of sebum was measured at the age of 80 days from the amount of skin-surface lipids that could be extracted with acetone and which had been produced during 2 days. Castration of rats at birth decreased the rate of sebum secretion and neonatal castration plus neonatal thyrotoxicosis produced an even lower level of sebum which more nearly approached that seen in female rats with neonatal T4 treatment. It was concluded that a reduction in the response of the sebaceous glands in adult rats made thyrotoxic with high doses of T4 in the early stage of life is not due to a decreased secretion of gonadal steroids.