Duration-dependent effect of transient neonatal hypothyroidism on sertoli and germ cell number, and plasma and testicular interstitial fluid androgenbinding protein concentration

The impact of transient neonatal hypothyroidism on growth and function of p uberal testis during different milestones of postnatal testicular developme nt was studied in Wister rats. Rat pups were made hypothyroid for 10, 15, 3 0, 40 and 60 days of postnatal age from birth by providing 0.05% (W/V) meth imazole (MMI) in the drinking water of the mother, from day 1 postpartum ti ll weaning (25 days postpartum) and thereafter in the drinking water. Contr ol rats were raised without MMI treatment. Sertoli cell number and its func tion was assessed on day 60 postpartum. Sertoli cell number increased consi stently in 10, 15, 30 and 40 days transient hypothyroid rats but decreased in rats subjected to continuous hypothyroidism from birth to 60 days postpa rtum. Rats subjected to continuous hypothyroidism from birth showed spermat ogenic arrest at puberty and had only a single layer of spermatogonia. Tran sient neonatal hypothyroidism for 10 (or) 15 days from birth increased sper matocytes (pachytene and zygotene), spermatids (elongated and round) wherea s, that of 30 and 40 days decreases the number of germ cells. Plasma androg en binding protein (ABP) concentration decreased in puberal rats belonging to all groups, whereas the testicular interstitial fluid (TIF) concentratio n of ABP increased significantly in 10 and 15 days hypothyroid rats while i t decreased in all other groups. These findings indicate that the mitogenic activity of Sertoli cell is increased irrespective of the duration of tran sient neonatal hypothyroidism. However, the functional activity of Sertoli cells (ABP production) in these puberal rats varies depending upon the post natal period at which the animals were in hypothyroid state.