Thyroid hormone supplements are primarily used to treat hypothyroidism , a condition caused by deficient secretion of thyroid hormone by the thyroid gland. Forms of thyroid hormone include:
- Dextrothyroxine (Choloxin)
- Levothyroxine (Levoid, Levothroid, Levoxine, Levoxyl, Synthroid)
- Liothyronine (Cytomel, Triostat)
- Liotrix (Euthroid, Thyrolar)
- Thyroglobulin (Proloid)
- Thyroid (Armour Thyroid)
Calcium Two case reports suggest that calcium carbonate interferes with the body's absorption of thyroid hormone when both were taken at the same time. 1,2 A prospective cohort study has validated these case reports. 3 Twenty individuals with hypothyroidism stabilized on long-term levothyroxine therapy were included in the trial. Participants were given calcium carbonate (1,200 mg daily of elemental calcium) for 3 months. During the period the calcium supplement was taken, thyroid hormone blood levels declined. But after calcium supplementation was stopped, thyroid levels climbed back up, slightly surpassing the levels measured at the beginning of the study. It is thought that calcium combines with thyroid hormone, thus reducing its absorption.To prevent this interaction, take thyroid hormone and calcium supplements as far apart as possible.
Iron Iron salts (including ferrous fumarate, ferrous gluconate, ferrous sulfate, and iron polysaccharide) may impair the effect of the thyroid hormone levothyroxine, probably by forming a complex with it and decreasing its absorption. 4To prevent a problem, take iron supplements and thyroid hormones as far apart as possible.