Parathyroid Hormone (PTH) Test

Parathyroid hormone, abbreviated as PTH, is also known as the life-saving hormone. The hormone regulates calcium balance in the body and is secreted by four parathyroid glands surrounding the thyroid gland. Calcium is necessary for the formation of teeth, bones, clotting, the release of hormones and the maintenance of the nervous system. The hormone targets the kidneys, intestines and bones. The primary purpose of the parathyroid hormone is to increase calcium levels. It is done via renal calcium resorption and decreasing phosphorus levels.

There are two possible scenarios:

• A low blood calcium level stimulates the parathyroid gland to release PTH in the blood. It results in a normal calcium level.
• A high blood calcium level causes negative feedback and parathyroid glands stop releasing PTH. It will cause a normal blood calcium level.

Any abnormalities in PTH can be detected using the PTH blood test. The test is compatible for both adults and children, irrespective of gender.

Your doctor will prescribe a PTH blood test if calcium or phosphorus abnormalities are suspected. Symptoms like increased thirst, nausea, vomiting, fatigue and abdominal pains state this fact. A person needs to fast for eight to twelve hours. They can consume water during this period before the PTH test. To summarise, the primary functions of PTH are:

• To regulate blood calcium levels 24x7.
• Phosphate regulation in the body.
• Synthesising active form of vitamin D.

India suffers from an over-functioning parathyroid gland, vitamin D deficiency and other bone disorders at a large scale due to a lack of awareness and negligence towards getting routine calcium screening examinations. An over-functioning parathyroid gland means hyperparathyroidism. It can result in kidney stones, depression, bone fractures, etc. Thus, getting examined routinely for calcium and parathyroid hormone is an intelligent decision towards leading a healthier lifestyle.

Other names for PTH Test

• PTH Blood Test
• Intact PTH
• Intact Parathyroid Hormone Test
• Parathormone Test

What does the PTH test detect or measure and who is this prescribed for?

The PTH blood test solely accounts for the PTH levels in the bloodstream. It is analysed based on a blood sample collected by the healthcare professional. The rise or fall of these levels has numerous interpretations. The PTH blood test is applicable for males and females, both adults and children.

The PTH test can help assess the following:

• Primary hyperparathyroidism
• Secondary hyperparathyroidism
• Tertiary hyperparathyroidism
• Tumour or cancer of the parathyroid gland
• Hypoparathyroidism
• Osteoporosis
• Hypocalcemic Tetany
• The definite cause behind high/low calcium levels
• Chronic renal failure

A PTH blood test is prescribed for those experiencing symptoms of impaired calcium levels:

Symptoms of hypercalcemia or high calcium levels:

• Increased urination
• Fatigue, headache and body aches
• Loss of appetite and constipation
• Nausea and vomiting
• Depression and lethargy
• Weakness and cramps

Symptoms of hypocalcemia or low calcium levels:

• Numbness and tingling sensations in the extremities
• Confusion and memory loss episodes
• Irregular heartbeat
• Increased occurrence of bone fractures
• Brittle nails
• Depression and hallucinations

Reference: Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic & Laboratory Test Reference. 14th ed. St. Louis, Mo: Elsevier; 2019.

Pregnancy and breastfeeding are normal physiological conditions that increase parathyroid hormone levels in the blood.

The results of the PTH test can help yield information about abnormal levels of PTH in women, men and children.

According to the American Board of Internal Medicine, normal values for PTH should lie between 10-65 picograms per millilitre (pg/mL). The test result will interpret whether you have hyperparathyroidism or hypoparathyroidism. Your PTH levels will be interpreted, keeping the calcium blood levels in mind.

The possible interpretations of PTH levels in the body are:

1. Hyperparathyroidism: This is due to elevated synthesis and release of PTH in the blood.

• Primary hyperparathyroidism
• Secondary hyperparathyroidism
• Tertiary hyperparathyroidism

The laboratory findings, in addition to increased PTH levels, are:

• Hypercalcemia in primary hyperparathyroidism.
• Increased serum alkaline phosphatase enzyme (ALP).
• Decreased phosphorus levels, known as hypophosphatemia.
• Vitamin D deficiency.

2. Hypoparathyroidism: There are lower than normal secretions of PTH in the blood. Features like severe muscle spasms, psychosis and epilepsy are seen.
3. Hypocalcemic tetany: It is a clinical manifestation of convulsion, coma and painful spasms.

The PTH blood test results are based on analysing a blood sample collected from the arm's vein.

Test Preparation

1. Before the test

The procedure for the PTH test requires overnight or eight to twelve hours of fasting. Here you cannot consume any solid food substances but are allowed to drink water. Also, avoid intake of particular medications, like:

• Calcium supplements, as they increase blood calcium levels
• Thiazide diuretics
• Vitamin D
• Thyroxine
• Consumption of excess milk or milk products before the test

2. During the test

A nurse or sample collector will use your arm's vein to collect the blood sample. Preferably, wear a short sleeve for convenience during sample collection.

3. After the test

When done hygienically and according to protocol, the intact PTH test procedure poses no serious threats to an individual. There might be a slight soreness due to needle insertion and lightheadedness.

Test inclusions: What parameters are included?

The PTH test only measures the level of parathyroid hormone in the blood. Although, it is also ordered to monitor chronic kidney diseases. The results of the PTH test must lie within the normal range to confirm a healthy functioning parathyroid gland. The PTH test accounts for the concerning signs and symptoms of hyperparathyroidism and hypoparathyroidism.

How frequently should you take this test?

A basal metabolic panel can detect abnormal calcium levels in the blood. With the help of these findings, your doctor can prescribe a follow-up PTH blood test to identify the cause behind the rise or fall of calcium levels.

Thus, a basal metabolic panel (BMP) done once a year will guide you towards your next steps. Otherwise, signs and symptoms like muscle spasms and cramps, bone pains and fractures or abdominal distress can also raise an issue with the parathyroid gland. If you are hypocalcemic, you should take appropriate medication. Upon reaching a stable calcium concentration in the blood, get monitored every three to six months.

Hyperparathyroidism, Hypoparathyroidism, Osteoporosis, Hypocalcemic tetany