Hypothyroidism and Fertility: An Animal Model follows up in The Second-Generation

Hypothyroidism is known as the most common endocrine disorder. The prevalence of hypothyroidism in the female and male population is 2% and 0.2%, respectively. Maternal hypothyroidism is a defect in the thyroid hormones transition from the mother to the fetus. The present study was conducted to find whether maternal hypothyroidism affects the fertility of the second generation.

In this experimental study, twelve adult female rats weighting 180-220 g were randomly divided into case and control groups. Hypothyroidism was induced by dissolving 0.1 g/L of 6-n-propyl-2-thiouracil in drinking water toward the end of pregnancy and lactation. At the end of the breastfeeding period, the blood samples of female children were collected. Six healthy, mature, female rats were selected and kept until they reached maturity, and were then mated with male rats. After observing the female rats' delivery, blood samples were collected from their male and female newborns and the healthy rats were selected.

There was a significant difference in the volume and size of ovarian as well as in the number of secondary follicles in comparison with the control group (P=0.025). However, there were no significant changes in the other parameters including the number of primary follicles, the number of Graafian follicles and sperm parameters. There was no significant decrease in the testicular volume and size, number of Leydig cells and seminiferous tubules diameter.

Maternal hypothyroidism has no significant effects on testicular tissue function, and sperm parameters in the second generation, but can significantly reduce the rate of secondary follicles in the second generation female rats.