Thyroid function alterations attributed to high iodide supplementation in maternal rats and their offspring.

Area of Science:

• Endocrinology
• Toxicology
• Reproductive Biology

Background:

• Iodide is essential for thyroid hormone synthesis, but excessive intake can disrupt thyroid function.
• Maternal thyroid status significantly impacts fetal and offspring development.
• Understanding the effects of high iodide supplementation is crucial for maternal and child health.

Purpose of the Study:

• To investigate the impact of high iodide supplementation during pregnancy and lactation on maternal and offspring thyroid function.
• To assess thyroid hormone levels, iodine content, oxidative stress, and gene expression in response to varying iodide intakes.
• To determine the long-term effects of prenatal and early-life iodide exposure on thyroid health in offspring.

Main Methods:

• Pregnant rats were divided into normal iodide intake (NI), 10x high iodide (10 HI), and 100x high iodide (100 HI) groups.
• Maternal urine, milk, thyroid, and mammary gland tissues were analyzed for iodine concentration, oxidative stress, and specific gene expression (TRα1, TRβ1, NIS, Dio1).
• Offspring were exposed to different iodide levels from weaning to postnatal day 180 (PN180), with serum thyroid hormones and antibodies measured.

Main Results:

• High iodide intake (10 HI and 100 HI) significantly increased iodine concentration in maternal tissues and milk.
• Maternal rats in the 100 HI group exhibited altered thyroid hormones (low FT3, high FT4), increased thyroid antibodies (TPOAb, TgAb), elevated mitochondrial superoxide production, and decreased expression of key thyroid-related genes.
• Offspring exposed to 10 HI and 100 HI showed decreased FT3 and FT4 levels, and increased TSH, TPOAb, and TgAb at PN180, indicating hypothyroidism and thyroiditis.

Conclusions:

• Maternal normal thyroid function can be maintained with 10x high iodide intake, but 100x high iodide intake induces thyroiditis during lactation.
• Offspring exposed to both 10x and 100x high iodide levels develop hypothyroidism complicated with thyroiditis by adulthood (PN180).
• Excessive iodide supplementation during gestation and lactation poses significant risks to maternal and offspring thyroid health, necessitating careful dosage monitoring.