PTH (Parathyroid Hormone)
Parathyroid hormone is produced by the four parathyroid glands behind the thyroid. It raises blood calcium by pulling calcium from bone, increasing kidney calcium reabsorption, and activating vitamin D for gut calcium absorption. PTH is measured alongside calcium, phosphorus, and vitamin D to work up hyperparathyroidism, hypocalcemia, chronic kidney disease-related bone disease, and osteoporosis. Intact PTH (iPTH) is the standard assay.
Reference Ranges
Male
15 – 65
pg/mL
Female
15 – 65
pg/mL
Child
15 – 65
pg/mL
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low PTH with low calcium suggests primary hypoparathyroidism — after thyroid or parathyroid surgery, autoimmune destruction, DiGeorge syndrome, or magnesium deficiency (magnesium is needed for PTH secretion). Symptoms: tingling around the mouth and fingertips, muscle cramps, carpopedal spasms, seizures in severe cases. Treatment is calcium and calcitriol (activated vitamin D).
What High Levels Mean
High PTH with high calcium is the hallmark of primary hyperparathyroidism — usually a single parathyroid adenoma; occasionally four-gland hyperplasia or parathyroid carcinoma. Surgery is curative. High PTH with low or normal calcium is secondary hyperparathyroidism — due to vitamin D deficiency, chronic kidney disease, or malabsorption — treated by correcting the underlying cause. Very high PTH in CKD patients suggests tertiary hyperparathyroidism.
Frequently Asked Questions
What is the most common cause of high PTH in India?
Vitamin D deficiency, which is extremely common in Indians of all ages. Low vitamin D reduces gut calcium absorption, which raises PTH (secondary hyperparathyroidism). Correcting vitamin D deficiency normalizes PTH in most cases. If PTH stays high after adequate vitamin D repletion, primary hyperparathyroidism should be considered.
Does PTH need to be tested with calcium?
Yes — always. PTH alone cannot distinguish primary from secondary hyperparathyroidism. The combination of PTH, calcium, phosphorus, and 25-hydroxy vitamin D makes the diagnosis: high Ca + high PTH = primary; low or normal Ca + high PTH = secondary. Ionized calcium is more accurate when albumin is abnormal.
When is parathyroid surgery recommended?
Symptomatic primary hyperparathyroidism (osteoporosis, kidney stones, overt hypercalcemia symptoms) is surgery. For asymptomatic primary hyperparathyroidism, surgery is recommended if: age <50, calcium >1 mg/dL above upper limit, eGFR <60, osteoporosis (T-score ≤ -2.5) or vertebral fracture, urinary calcium >400 mg/day, or kidney stones. Minimally invasive parathyroidectomy has excellent cure rates in experienced centers.
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nmol/LThis information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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