Calcitonin

Calcitonin is a hormone from thyroid parafollicular (C) cells that helps lower blood calcium. It inhibits osteoclast-mediated bone resorption, promotes calcium deposition into bone, and increases renal excretion of calcium and phosphate. Calcitonin acts as a short-term regulator of calcium levels (less influential than parathyroid hormone) and is used therapeutically for hypercalcemia, Paget’s disease, and some osteoporosis cases.

Calcitonin decreases blood calcium levels. Secreted by thyroid C cells, it inhibits osteoclast-mediated bone resorption and reduces renal calcium reabsorption, increasing urinary calcium excretion. Clinically it’s used short-term to treat hypercalcemia and disorders like Paget’s disease; its hypocalcemic effect is modest and generally shorter-lasting than regulation by parathyroid hormone and vitamin D.

Calcitonin is a hormone medication used to slow bone resorption and treat conditions with excessive bone breakdown or high calcium. Clinically it's used for postmenopausal osteoporosis (to reduce vertebral fracture risk and relieve pain), Paget’s disease of bone, and acute hypercalcemia. It’s available as a nasal spray or injection and is typically used short-term or when other therapies are unsuitable.

Basal calcitonin above about 100 pg/mL is highly suggestive of medullary thyroid carcinoma. Levels between roughly 10–100 pg/mL are indeterminate and usually prompt stimulation testing and imaging. Very high values (often >500 pg/mL) commonly indicate metastatic disease. Interpretation depends on sex-specific reference ranges, assay method and clinical context; specialist assessment is recommended.

Calcitonin secretion is mainly triggered by high blood calcium. Eating calcium-rich foods—dairy (milk, yogurt, cheese), fortified plant milks, leafy greens (kale, broccoli), sardines, tofu, almonds and sesame—can transiently raise calcium and stimulate calcitonin. Protein-containing meals also produce modest postprandial increases. Maintain balanced calcium and vitamin D intake and consult a clinician before using supplements or treating thyroid-related concerns.

High blood calcium (hypercalcemia) is most often caused by primary hyperparathyroidism or cancers (including bone metastases or PTH-related protein). Other causes include excessive vitamin D or calcium intake, granulomatous diseases (e.g., sarcoidosis), certain drugs such as thiazide diuretics, dehydration, and rare genetic conditions like familial hypocalciuric hypercalcemia. Endocrine disorders (e.g., hyperthyroidism) can also contribute; prompt medical evaluation identifies the cause.