Parathyroid Hormone (PTH)

Special Precautions/Comments:

Please send EDTA plasma sample alongside separate serum sample for other biochemistry including calcium.

Additional Information:

Parathyroid hormone (PTH) is produced and secreted by chief cells in the parathyroid gland and plays an important role in calcium homeostasis. PTH is secreted in response to low serum calcium and acts to increase serum calcium levels by increasing bone resorption and calcium reabsorption in the kidney (at the expense of phosphate). PTH also upregulates 1-alpha hydroxylase activity in the kidney, increasing production of 1,25-vitamin D, which acts to increase intestinal absorption of calcium and phosphate. When calcium levels normalize, PTH secretion is stopped via negative feedback on the parathyroid. Any residual PTH is metabolised and cleared by the liver and kidneys.  

In hyperparathyroidism, this regulation is lost and PTH is increased. In primary hyperparathyroidism, excess PTH is inappropriately secreted in the absence of a low serum calcium. In secondary hyperparathyroidism, the PTH is increased in the presence of a low serum calcium due to the presence of kidney, liver or bowel disease. One of the most common causes of secondary hyperparathyroidism is vitamin D deficiency.

In hypoparathyroidism, low serum calcium is present in the absence of PTH. Causes include magnesium deficiency (magnesium is required for PTH secretion), removal of the parathyroid, damage to the parathyroid (surgical, irradiation) or an infiltrative disease such as haemochromatosis, Wilson’s disease or metastasis.