[Modifying effect of thyroid gland functional disorders on realization of transplacental carcinogenesis induced by...

The paper discusses the influence of deranged function of the thyroid (in postnatal period) on the transplacental carcinogenic effect of N-nitrosomethylurea (NMU) in albino noninbred rats. It was found that exogenous thyroxin-induced hyperthyroidism and thyroid function suppression either by long-term treatment with a thyreostatic agent--methylthiouracil (MTU) or thyroidectomy are followed by a lower frequency of, chiefly, nervous system tumors which are typical of NMU-induced transplacental carcinogenesis in rats. Moreover, transplacental treatment with NMU potentiated the carcinogenic effect of MTU on the thyroid. The latter manifested itself in a higher frequency of malignancies of the thyroid in animals exposed to a combined treatment with NMU (transplacentally) and MTU (postnatally) as compared with those given MTU only (postnatally).