Hyperparathyroidism Diagnostic Tests

The two primary tests used to diagnose primary hyperparathyroidism are blood calcium levels and blood parathyroid hormone levels (PTH).  It is important to understand the relationship between blood calcium level and parathyroid hormone. When the blood calcium level is high, the parathyroid hormone should be low.  A high calcium level with a parathyroid hormone level that is either elevated or in the high normal range usually indicates primary hyperparathyroidism.  It is also important to understand that both the parathyroid hormone level and calcium levels change with time so it may be required to do several calcium and PTH tests before confirming the diagnosis.   Other tests then help confirm the diagnosis of primary hyperparathyroidism.

A 24 hour urine calcium level that is elevated also supports the diagnosis of primary hyperparathyroidism.  When there is excessive calcium being broken down from the bones, there is frequently elelvated calcium level over a 24 hour period in the urine.  An elevated calcium level in the urine is not normal.

Vitamin D level helps determine if hyperparathyroidism is in fact secondary rather than primary.   Vitamin D deficiency is one of the reasons for calcium deficiency and excess parathyroid hormone secretion.

Serum phophate is usually low due to excessive secrtion and loss of the body's phosphorus through the kidneys.  There is decreased reabsorption of phosphorus by the kidneys in primary hyperparathyroidism.  This contrasts with secondary hyperparthyroidism, where the phosphate levels are generally elevated.

Imaging tests that help localize and confirm the presence of a parathyroid adenoma include the parathyroid sestambi scan and high resolution ultrasound of the thyroid and parathryoid glands.