Impact of neonatal hypothyroidism on Leydig cell number, plasma, and testicular interstitial fluid sex steroids concentration

We have previously demonstrated that neonatal and transient neonatal hypoth yroidism modulates Leydig, Sertoli, and germ cell numbers, sex steroids and androgen binding protein concentration. The present study was undertaken t o study the effect of neonatal onset hypothyroidism on Leydig and peritubul ar myoid cell numbers, plasma and testicular interstitial fluid (TIF) sex s teroid concentration at different age groups of Wistar rats. Hypothyroidism was induced by giving 0.05% methimazole (MMI) to lactating mothers or dire ctly to the male pups from day 1 postpartum through days 10, 15, 30, 40 and 60 postpartum. To confirm hypothyroidism, plasma thyroid hormones and TSH were assayed. Plasma and TIF testosterone, progesterone, dihydrotestosteron e (DHT) and estradiol were assayed by radioimmunoassay. Leydig cell number in hypothyroid rats were less than the age-matched controls. The diameter o f Leydig cells in hypothyroid rats was smaller than the controls but 10 day s old hypothyroids alone had larger than control rats. A significant decrea se of peritubular myoid cell number was observed in 30, 40 and 60 days hypo thyroid rats and increased in 10 and 15 days hypothyroidism. Hypothyroid ra ts had elevated level of plasma LH and decreased GH (except day 10 postpart um). Plasma PRL level was increased in 10 and 15 days hypothyroid rats and an opposite effect was observed in 40 and 60 days hypothyroidism. Plasma te stosterone, DHT and estradiol were decreased in all hypothyroid rats. Howev er, plasma progesterone level in hypothyroid rats was significantly higher at days 10, 30, and 40 postpartum and an opposite effect was seen in 15 and 60 days experimental groups. TIF testosterone and progesterone titre showe d a consistent decrease in hypothyroid rats irrespective of the duration. I n hypothyroid rats, TIF DHT levels decreased significantly in days 10, 40 a nd 60 postpartum. However, it increased in days 15 and 30 postpartum. Excep t at day 10 postpartum, the level of TIF estradiol in hypothyroid rats was significantly less than their age matched controls. Our data clearly indica te that neonatal onset hypothyroidism adversely affect Leydig cell prolifer ation along with impaired steroidogenesis.