Impact of foetal-onset hypothyroidism on the epididymis of mature rats.
It is well established that congenital hypothyroidism leads to male infertility. However, there is a dearth of information on foetal-onset hypothyroidism-induced changes in the epididymis. With regard to transient hypothyroidism, the existing literature deals mainly with the testis. However, it is not known whether there is any corresponding alteration in epididymal morphology and physiology under such a condition. The present study is therefore aimed at understanding the impact of persistent and transient hypothyroidism on the concentration of epididymal sex steroids, as they play a vital role in maintaining the normal structure and function of the epididymis. Normal rats of 90 days of age served as controls (Group I). Hypothyroidism was induced by using pregnant/lactating mothers and post-weaning rats to 0.05% (w/v) methimazole (MMI) in the drinking water. Group II were subjected to persistent hypothyroidism from day 9 of post-coitum (pc) to 90 days. Group III rats were subjected to transient hypothyroidism from day 9 day pc to day 1 post-partum (pp), 21 pp or 35 pp (IIIa, b and c, respectively) and group IV rats were given simultaneous T3 supplementation (3 microg/100 g body wt./day i.m.) with MMI from day 9 pc to day 1 pp; 21 pp and 35 pp (Group IVa, b and c). Animals from all groups were killed on day 90 pp. Serum thyroid stimulating hormone (TSH) and thyroid hormones confirmed euthyroidism in group I, IIIa, b and c and IVa, b and c rats and hypothyroidism in group II rats. Caput and cauda epididymal concentration of testosterone, dihydrotestosterone (DHT), estradiol (E2) and androgen binding protein (ABP) markedly decreased in group II rats. While the concentration of testosterone, E2 and ABP increased in group III rats, that of DHT remained unaltered. However, group IV rats maintained normal concentration of the sex steroid and ABP. The activity of 5-alpha-reductase in the epididymis of all the groups followed the same trend as that of the concentration of epididymal DHT. From the present data it is evident that persistent hypothyroidism diminishes the bioavailability of androgens and oestrogens, while transient hypothyroidism enhances the same, indicating the importance of euthyroidism during foetal and neonatal period towards the maintenance of optimal hormonal status in the epididymis required for its maturation.
Kala
N
N
Department of Endocrinology, Dr ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai 600 113, Tamil Nadu, India. kala_natarajan@hotmail.com
Ravisankar
B
B
Govindarajulu
P
P
Aruldhas
M M
MM
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism; D000818:Animals; D013196:Dihydrotestosterone / Q000378:metabolism; D004822:Epididymis / Q000196:embryology* / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism; D005260:Female; D012739:Gonadal Steroid Hormones / Q000378:metabolism; D007037:Hypothyroidism / Q000196:embryology* / Q000473:pathology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013739:Testosterone / Q000378:metabolism; D013972:Thyrotropin / Q000097:blood
D012739:Gonadal Steroid Hormones; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol; D013972:Thyrotropin; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase