Parathyroid hormone (PTH) is a key hormone produced by the parathyroid glands, small glands located in the neck behind the thyroid.

Its main role is to regulate calcium levels in the blood, bones, and kidneys.

• It increases the absorption of calcium in the intestines.
• It encourages the kidneys to retain calcium.
• It stimulates the release of calcium from bones into the bloodstream.

When calcium levels in the blood are too low, the parathyroid glands release more PTH to restore normal levels. Conversely, when calcium is too high, PTH levels decrease.

PTH tests are important for diagnosing conditions linked to abnormal calcium levels, such as hyperparathyroidism, kidney disease, and bone disorders.

A PTH test is usually prescribed when a calcium imbalance or a condition affecting the parathyroid glands is suspected. This test helps determine if the parathyroid glands are working properly and contributing to abnormal calcium levels.

PTH testing is recommended in the following cases:

• Abnormal calcium levels : Calcium that is too high or too low was detected in blood tests.
• Bone pain or weakness : In case of unexplained bone pain or weakness.
• Kidney stones : Frequent stones may indicate abnormal calcium metabolism.
• Muscle fatigue or weakness : These symptoms may be related to an imbalance in calcium or PTH.
• Frequent urination and excessive thirst : These signs may indicate kidney problems related to a calcium imbalance.
• Numbness or tingling in the limbs : This can happen when calcium levels are too low.

PTH levels are usually measured by a blood test, where a sample is taken from a vein, usually from the arm.

In many cases, PTH is tested at the same time as calcium levels because these two elements are closely linked. This combined approach helps determine whether abnormal calcium levels are caused by parathyroid gland dysfunction or another underlying condition.

Common panels including PTH testing:

• Complete metabolic panel (CMP)
• Parathyroid panel (specific for PTH)

Preparations:
No special preparation is usually required, but your doctor may ask you to fast for a few hours before the test, depending on other tests done at the same time.

Normal PTH levels vary slightly depending on age and other factors such as pregnancy. Here are the general ranges:

• Kids :
  • Up to 1 year: 8.0-61 pg/mL
  • Up to 10 years: 11-59 pg/mL
  • Up to 17 years: 11.4-14.3 pg/mL
• Adults : 15-65 pg/mL
• Pregnant women :
  • Up to 12 weeks: 10-15 pg/mL
  • Up to 27 weeks: 18-25 pg/mL
  • Up to 42 weeks: 9-26 pg/mL

Note : The units of measurement and the normal ranges may differ depending on the laboratory and the specific methods used.

High PTH levels
High levels of PTH indicate that the body is trying to increase calcium levels in the blood, often due to an underlying condition.

Causes of high levels:

• Primary hyperparathyroidism: Overactive parathyroid glands that produce too much PTH.
• Kidney disease: Reduced kidney function can cause calcium to fall, causing PTH to rise.
• Vitamin D Deficiency: Low levels of vitamin D can stimulate PTH production.
• Bone disorders: Like osteomalacia, where weakened bones cause PTH to rise.
• Specific cancers: Some cancers, such as kidney or lung, can produce proteins similar to PTH.

Recommendations:

• Consult a doctor to identify the underlying cause.
• Monitor your calcium and vitamin D levels regularly.
• Maintain physical activity to strengthen bones.
• Eat a balanced diet rich in calcium, but avoid excesses without medical advice.

Low PTH levels
Low PTH levels suggest reduced parathyroid gland activity or another condition that suppresses PTH production.

Causes of low levels:

• Primary hypoparathyroidism: Insufficient production of PTH, often due to autoimmune diseases or surgical removal.
• Magnesium Deficiency: Low levels of magnesium can alter the function of the parathyroid glands.
• Autoimmune disorders: Some diseases attack the parathyroid glands.
• Hypercalcemia: High levels of calcium naturally lower PTH.

Recommendations:

• Have your calcium levels checked regularly.
• Incorporate foods that are rich in calcium and magnesium into your diet.
• Work with a healthcare professional to restore PTH balance.
• Avoid overconsumption of vitamin D and calcium without medical advice.

If you have abnormal PTH levels or symptoms related to a calcium imbalance, see a endocrinologist. Endocrinologists specialize in the body's glands and hormones and can provide a detailed diagnosis and treatment plan tailored to your PTH levels.