Effect of Prenatal Vitamin D and Selenium Supplementation on Minipuberty in Male Offspring of Women with Autoimmune Thyroiditis

Background/Objectives: Minipuberty represents the second phase of physiological activation of the reproductive axis and may play a role in postnatal genital development. Its course has been shown to be affected by untreated or inadequately treated maternal hypothyroidism. The aim of the present study was to investigate minipuberty in the sons of women with euthyroid autoimmune thyroiditis during pregnancy. Methods: This prospective matched cohort study included three groups of apparently healthy infant boys. Two groups comprised the male offspring of levothyroxine-naive, euthyroid women with autoimmune thyroiditis: one group was unsupplemented, and the other received vitamin D and selenium supplementation. The control group consisted of boys born to healthy women. Salivary concentrations of testosterone, androstenedione, DHEA-S, estradiol, and progesterone, along with urinary FSH and LH levels, were assessed longitudinally over the first 12 months of life. These hormonal measurements were evaluated in relation to genital development, including testicular volume and penile length, which were recorded at each study visit. Results: Compared with the offspring of healthy mothers, sons of women with autoimmune thyroiditis who did not receive supplementation exhibited lower concentrations of LH and testosterone, without a distinct peak, while the duration of hormone detectability did not differ between the groups. These hormonal alterations were accompanied by reduced penile length, with no differences observed in testicular volume. This group also exhibited lower DHEA-S concentrations, whereas levels of other hormones were comparable. In contrast, in the group receiving vitamin D and selenium supplementation, the dynamics of hormonal changes and genital organ growth did not differ from those observed in the control group. LH concentrations were inversely correlated with thyroid peroxidase antibody titers, which were lower in the supplemented group. Conclusions: The findings indicate an altered course of minipuberty in the sons of women with euthyroid autoimmune thyroiditis during pregnancy and suggest a potential benefit of exogenous vitamin D and selenium supplementation in this population.