Thyroid Hormones

Thyroid Hormones/Nutrient Depletion:

  • CalciumCalcium: Based on human evidence, thyroid hormones may increase urinary loss of calcium (2023349). Levothyroxine may adsorb (stick) to calcium carbonate in an acidic environment, which may block its absorption. In a human study, patients undergoing long-term treatment with thyroxine showed a higher concentration of serum alkaline phosphatase, osteocalcin, urinary calcium/creatinine and hydroxyproline/creatinine (8931510).
  • IronIron: According to secondary sources, iron may decrease the absorption and efficacy of levothyroxine (Levoxyl?, Synthroid?) by forming insoluble complexes in the gastrointestinal tract.
  • MagnesiumMagnesium: Based on in vitro animal study, changes in thyroid hormone levels may have an effect on magnesium homeostasis (18604605). Supplementation of thyroid hormone to hypothyroid animals restored magnesium levels and transport. According to secondary sources, oral magnesium salts have been reported to chelate oral levothyroxine within the gastrointestinal tract when administered simultaneously, leading to decreased thyroid hormone absorption. To minimize this interaction, secondary sources advise administering thyroid hormones at least four hours before or after antacids or other drugs containing magnesium.
  • PhosphatePhosphate: A human study showed increased TNSALP, the gene that encodes "tissue-nonspecific" alkaline phosphatase (ALP) synthesis, in bone together with lowered extracellular concentrations of inorganic phosphate (a competitive inhibitor of ALPs) (17213282). In another human study, the mean daily urinary excretion of calcium and phosphate was increased in patients given a higher dose of human parathyroid hormone, hPTH-(1--34) (7298851).