PTH (Parathyroid Hormone) Test

A PTH test is recommended to individuals who get abnormal (high or low) calcium levels results in another blood test. This test is also performed if patients present with signs and symptoms of abnormal calcium levels.

Estimating PTH levels helps doctors to determine the cause of abnormal calcium levels in the body. Following are the signs and symptoms of low calcium levels (hypocalcaemia):

• Mood fluctuations or depression
• Muscle seizures and spasms
• Irregular heartbeat
• Numbness and tingling

 Following are the signs and symptoms of hypercalcaemia:

• Urinating frequently
• Weak bones
• Increased thirst
• Nausea
• Kidney stones
• Pains and aches
• Fatigue

The test is also conducted when low phosphorus levels, severe osteoporosis or kidney disease is observed.

PTH levels increase during sleep hours and reduce during mid-morning and late afternoon time. Hence, you should ask your healthcare provider if fasting is needed before the test. The levels might also fluctuate due to seasonal changes. Blood sample for this test is usually withdrawn during the late afternoon and mid-morning hours. Make sure to inform your doctor about the timing of the sample withdrawn

For a PTH test, a blood sample will be collected from a vein in your hand.

The likely risks associated with this blood test include bleeding, light-headedness, bruising and infection. However, most of these symptoms subside on their own. If you notice persistent discomfort, check in with a doctor as soon as possible.

The normal results vary among different laboratories as they depend on the measurements and test specimens used. Consult your doctor for the interpretation of results.

Normal results: Normal PTH levels range from 10 to 55 picograms per millilitre (pg/mL).

Abnormal results: Lower than normal PTH levels might indicate the following:

• Autoimmune destruction of the parathyroid gland
• Tuberculosis and sarcoidosis
• Low magnesium levels in the blood
• Excess vitamin D intake
• Accidental removal of the parathyroid gland during thyroid surgery
• The inability of the parathyroid glands to produce PTH
• Cancers that started in other body parts, such as the colon, breast and lungs, which have spread to the bone
• Effect of radiation on the parathyroid glands
• Excess sodium bicarbonate, certain antacids and calcium supplements

Higher than normal PTH levels might indicate the following:

• Pseudohypoparathyroidism (inability of the body to produce a response to PTH)
• Inadequate calcium absorption from the gut, insufficient calcium intake or loss of calcium through urine
• Swelling in the parathyroid glands
• Breastfeeding or pregnancy (rare cases)
• Disorders that increase phosphorous or phosphate levels in the blood, such as chronic kidney disease
• Adenomas (tumours in the parathyroid gland)
• Vitamin D disorders due to lack of sun exposure, problems in absorption, use or breakdown vitamin D in the body

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.