Hormone Biomarkers: Parathyroid Hormone (PTH)

Optimal Takeaways

Parathyroid hormone regulates calcium, phosphorus, and magnesium levels in the blood and facilitates the activation of vitamin D in the kidney.

Low levels are associated with damage to the parathyroid gland, metabolic dysfunction, bone tumors, and response to hypercalcemia. In contrast, elevated levels are associated with hypocalcemia, PTH tumors, vitamin D insufficiency, and increased CVD risk.

Standard Range: 10 - 65 pg/mL (1.06 - 6.9 pmol/L)

The ODX Range: 10 - 32 pg/mL (1.06 – 3.39 pmol/L)

Low levels of PTH occur in response to hypercalcemia due to vitamin D intoxication, milk-alkali syndrome, sarcoidosis, and metastatic bone tumors. Low levels are also seen with hypomagnesemia, hypoparathyroidism, autoimmune destruction of the parathyroid gland, Graves’ disease, milk-alkali syndrome, and DiGeorge syndrome. Medications that can decrease PTH include propranolol and cimetidine (Pagana 2021). Autoimmune destruction of the parathyroid gland, severe damage during thyroid surgery, and severe illness can reduce PTH levels even with low calcium levels (Khan 2021).

High levels of PTH occur in response to hypocalcemia caused by malabsorption or vitamin D deficiency, PTH-producing tumors, and hyperparathyroidism. Increased levels can also be seen in chronic renal failure, osteomalacia, rickets, and parathyroid gland, lung, or kidney cancer. Medications that can increase PTH include steroids, lithium, rifampin, isoniazid, and anticonvulsants­ (Pagana 2021).

Overview

Parathyroid hormone (PTH) is involved in the regulation of calcium, phosphorus, and magnesium levels. PTH increases calcium in the blood by promoting its uptake from the GI tract; increasing the reabsorption of calcium and decreasing the reabsorption of phosphate by the kidney; finalizing activation of vitamin D by the kidney; and stimulating the conversion of osteoblasts to osteoclasts that then release calcium from the bone into circulation. Investigation of an imbalance should include serum levels of PTH, calcium, vitamin D, magnesium, and albumin (Khan 2021).

Parathyroid hormone levels at the upper end of the standard range may be associated with significant metabolic consequences. In a multicenter prospective study of 490 individuals with normal calcium and phosphorus levels, PTH levels in those who were vitamin D replete had a median of 31.9 pg/mL (3.4 pmol/L). Those with vitamin D insufficiency had a median PTH of 35.5 pg/mL (3.8 pmol/L), and those with frank vitamin D deficiency had a median PTH of 39.8 pg/mL (4.2 pmol/L) (Yalla 2019).

In one observational study, a PTH level above 49.5 pg/mL (5.25 pmol/L) was associated with significantly decreased 25(OH)D and increased cardiovascular risk characterized by significantly greater blood pressure, glucose, LDL cholesterol, and BMI (Pascale 2018). PTH levels were significantly higher in prostate cancer patients, with a mean level of 41.67 pg/mL (4.42 pmol/L) versus those diagnosed with benign prostatic hypertrophy with a mean PTH of 17.32 pg/mL (1.84 pmol/l) (Kim 2020)

A retrospective cohort study of hyperparathyroidism patients undergoing parathyroidectomy found that PTH of 40 pg/mL or below was associated with the lowest risk of persistent disease (Claflin 2019).

References

Claflin, Jake et al. “Intraoperative parathyroid hormone levels ≤40 pg/mL are associated with the lowest persistence rates after parathyroidectomy for primary hyperparathyroidism.” Surgery vol. 166,1 (2019): 50-54. doi:10.1016/j.surg.2019.01.024

Khan, Maqsood, et al. “Physiology, Parathyroid Hormone.” StatPearls, StatPearls Publishing, 27 September 2021.

Kim, Won Tae et al. “Parathyroid hormone is associated with prostate cancer.” Prostate international vol. 8,3 (2020): 116-120. doi:10.1016/j.prnil.2020.02.002

Pagana, Kathleen Deska, et al. Mosby's Diagnostic and Laboratory Test Reference. 15th ed., Mosby, 2021.

Pascale, Antonietta V et al. “Vitamin D, parathyroid hormone and cardiovascular risk: the good, the bad and the ugly.” Journal of cardiovascular medicine (Hagerstown, Md.) vol. 19,2 (2018): 62-66. doi:10.2459/JCM.0000000000000614

Yalla, N et al. “Parathyroid hormone reference ranges in healthy individuals classified by vitamin D status.” Journal of endocrinological investigation vol. 42,11 (2019): 1353-1360. doi:10.1007/s40618-019-01075-w