Calcium-Phosphorus Metabolism in Females with Autoimmune Thyroiditis and Hypothyroidism

Thyroid dysfunction is frequently associated with disturbances of calcium and phosphorus homeostasis. Previous studies on bone and mineral metabolism in women with autoimmune thyroiditis (AIT) and hypothyroidism have conflicting results. The aim of the present work was to study the parameters of calcium-phosphorus metabolism in women with newly diagnosed autoimmune hypothyroidism and to compare them with those of the control group of healthy women. The study included 64 women with newly diagnosed autoimmune hypothyroidism. A comparison was made with the data of 75 age-, BMI- and menopausal state-matched healthy women. FT3, FT4, TSH, TPO-Ab, TG-Ab, total and ionized serum calcium, inorganic phosphate, magnesium, parathyroid hormone (PTH) and 25(OH) vitamin D were studied. Total and ionized calcium were lower in hypothyroid women in the absence of statistically significant difference compared to the controls. Intergroup analysis revealed no differences in serum phosphorus and 25(OH)D levels. Serum magnesium and PTH were significantly higher in hypothyroid group. These results coincide with some of the studies that examine the parameters of bone and mineral metabolism in hypothyroidism. Bone turnover is suppressed due to impaired mobilization of calcium from the bone, leading to decreased serum calcium levels and elevated PTH. We found a significant effect of thyroid hormones on magnesium homeostasis. The study did not find differences in vitamin D status between the groups. The observed inverse correlation between 25(OH)D and TgAb supports the concept of pathogenic relationship between vitamin D and the development of AIT.