Impact of experimental hypothyroidism and treatment with levothyroxin and zinc on the testis of adult albino rat: histological and immunohistochemical study

ABSTRACT

This study was performed to investigate the effects of experimental hypothyroidism on the testis and serum zinc level of adult rat and to compare the results of the different treatment regimens of levothyroxin and zinc. Twenty-five adult male albino rats were used. They were divided into group I [control group] with five animals and Group II [experimental group] with twenty animals. All animals of group II received daily intraperitoneal injections of propyl-thiouracil for three weeks for induction of hypothyroidism. The rats were then divided into four equal subgroups which were given levothyroxin and/or zinc sulphate supplementation or no further treatment for the next two weeks. Serum levels of T3, T4, TSH and zinc were evaluated for all animals in days 22 and 36 from the beginning of the experiment. At the end, testes were collected and paraffin sections were prepared. The sections were stained with H and E, PAS reaction and immunohistochemical staining for proliferating cell nuclear antibodies [PCNA]. PCNA-labeling index was calculated to assess spermatogenesis. It was concluded that [i] serum zinc levels were significantly decreased in hypothyroid rats and testicular histology was affected in the form of decreased diameter and narrowing of the seminiferous tubules, interstitial oedema, congestion of the blood vessels, thickening of the basement membrane and decreased spermatogenesis; [ii] oral zinc per se had no effect of the testicular histology or spermatogenesis; [iii] treatment with levothyroxin alone increased serum zinc levels and spermatogenesis without reaching control levels; [iv] zinc deficiency might add to the detrimental effects of hypothyroidism in spermatogenesis and [v] optimal results were achieved with combined levothyroxin and zinc replacement therapy. It was recommended to assess thyroid hormone levels routinely in cases of male infertility. Also, further studies for the interactions between thyroid gland disorders and zinc homeostasis were suggested