Effect of hypothyroidism induced by propylthiouracil and thiourea on male and female reproductive systems of neonatal mice

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Abstract
The effect of hypothyroidism induced by 6‐propyl‐2‐thiouracil (PTU) or thiourea (TU) on the development of the reproductive system in male and female neonatal ICR mice was investigated. PTU or TU was injected subcutaneously into experimental animals from postnatal day 1 (PD1) onward. The histological changes of the reproductive organs, formation of ovarian follicles, and spermatogenesis were examined on PD 14, 21, and 28, and the fertility of the hypothyroid mice in adulthood was followed. It was found that PTU or TU treatment did not produce an effect on the histology of the neonatal uterus and oviduct. In contrast, the drugs induced a decrease in the number of primordial follicles, multilaminar follicles, and Graafian follicles in the ovary. The number of follicles with degenerated follicular cells was increased. In the testis both PTU and TU treatments brought about a decrease in the number of seminiferous tubules with developing spermatids although the mean diameter of seminiferous tubules and the histology of the testis, epididymis, seminal vesicle, and coagulating gland was unaffected. The mating between hypothyroid females and euthyroid males and that between hypothyroid males and euthyroid females were normal with regard to the pregnancy rate, litter size, and sex ratio of offspring. The somatic growth of the resulting offspring was normal. It is concluded that the retarding effect on ovarian and testicular development in mice during neonatal period was not serious enough to adversely affect reproduction in the hypothyroid animals.