Parathyroid hormone (PTH) is a peptide produced by the parathyroid gland. PTH principally serves in the maintenance of calcium homeostasis; thus, assessment of PTH can be an important diagnostic aid for diagnosis of calcium metabolism disorders. In healthy individuals, PTH is secreted from the parathyroid gland as a negative feedback response to circulating calcium ion levels. The half-life of intact PTH is 2 to 5 minutes.
Hypercalcemia may be due to hyperparathyroidism, a group of conditions characterized by an overproduction of PTH. Hyperparathyroidism is separated into primary, secondary, and tertiary causes. Primary hyperparathyroidism is most frequently due to a parathyroid tumor (usually benign) that secretes PTH without feedback control, leading to hypercalcemia, kidney stones, calcium deposits in organs, and decalcification of bone. With primary hyperparathyroidism, patients will generally have high calcium and high PTH levels, while phosphate levels are often low.
Secondary hyperparathyroidism is usually due to kidney failure. In secondary hyperparathyroidism, patients will generally have high PTH levels and low or normal calcium levels. Sometimes, persons with secondary hyperparathyroidism develop high serum calcium and still have high PTH; this is sometimes called tertiary hyperparathyroidism.
Hypocalcemia may be due to hypoparathyroidism or a failure of the parathyroid gland to produce sufficient PTH. Hypoparathyroidism may be due to a variety of conditions and may be persistent, progressive, or transient. Causes include an autoimmune disorder, parathyroid damage or removal during surgery, a genetic condition, and severe illnesses. Affected patients will generally have low PTH levels and low calcium levels and will also have high phosphate levels.
Note: because of the physiological relationship of circulating calcium and PTH, it is always important to interpret PTH results in association with serum calcium.
|Plasma (EDTA):||1.0-5.0 pmol/L|
Chemiluminescent enzyme-labeled immunometric assay, ELISA.
Fasting morning specimen preferred.
Place on ice; refrigerate during centrifugation, and freeze immediately.
Comprehensive Metabolic Panel (see CMP for listed tests), Calcitonin, Albumin, Creatinine, Phosphorous, Calcium, Magnesium, Vitamin D-25-Hydroxy, Thyroid Stimulating Hormone, Ellsworth-Howard test.
|C41||Malignant neoplasm of bone and articular cartilage of other and unspecified sites|
|C41.9||Malignant neoplasm of bone and articular cartilage, unspecified|
|C74||Malignant neoplasm of adrenal gland|
|C74.0||Malignant neoplasm of cortex of adrenal gland|
|C74.1||Malignant neoplasm of medulla of adrenal gland|
|C74.9||Malignant neoplasm of unspecified part of adrenal gland|
|C74.90||Malignant neoplasm of unspecified part of unspecified adrenal gland|
|C74.91||Malignant neoplasm of unspecified part of right adrenal gland|
|C74.92||Malignant neoplasm of unspecified part of left adrenal gland|
|E04.1||Nontoxic single thyroid nodule|
|E04.2||Nontoxic multinodular goiter|
|E05.1||Thyrotoxicosis with toxic single thyroid nodule|
|E05.2||Thyrotoxicosis with toxic multinodular goiter|
|E25.0||Congenital adrenogenital disorders associated with enzyme deficiency|
|E25.8||Other adrenogenital disorders|
|E25.9||Adrenogenital disorder, unspecified|
|E55||Vitamin D deficiency|
|E55.9||Vitamin D deficiency, unspecified|
|I10||Essential (primary) hypertension|
|I99||Other and unspecified disorders of circulatory system|
|M83.2||Adult osteomalacia due to malabsorption|
|M83.5||Other drug-induced osteomalacia in adults|
|M83.8||Other adult osteomalacia|
|M83.9||Adult osteomalacia, unspecified|
|M89||Other disorders of bone|