Dietary calcium induced cytological and biochemical changes in thyroid

Certain epidemiological studies revealed correlation between hard water consumption (with high calcium) and thyroid size of the population, though the possible alterations in thyroid physiology upon calcium exposure are still inconclusive. Adult male Wistar strain rats were subjected to calcium treatment at the doses of 0.5 g%, 1.0 g% and 1.5 g% calcium chloride (CaCl2) for 60 days. The parameters studied were – thyroid gland weight, histopathology, histomorphometry; thyroid peroxidase (TPO), 5′-deiodinase I (DI), sodium–potassium adenosine triphosphatase (Na+–K+-ATPase) activities; serum total and free thyroxine (tT4, fT4), total and free triiodothyronine (tT3, fT3), thyroid stimulating hormone (TSH) levels. Enlargement of thyroid with hypertrophic and hyperplastic changes, retarded TPO and 5′-DI but enhanced Na+–K+-ATPase activities, augmented serum total and free T4 and TSH but decreased total and free T3 levels and low T3/T4 ratio (T3:T4) were observed in the treated groups. All these findings indicate development of goitrogenesis upon exposure to excessive dietary calcium.

► High calcium caused enlarged thyroid gland with hypertrophic/hyperplastic changes.
► Excess calcium decreased TPO and 5′ DI but increased Na+–K+-ATPase activities.
► Calcium altered serum total and free T4, total and free T3, T3/T4 ratio and TSH.
► Chronic calcium exposure exerted goitrogenic or antithyroidal action.