15 Common Causes of High Parathyroid Hormone

2. Low Vitamin D

Low vitamin D is a common cause of high parathyroid hormone (PTH). Your body needs vitamin D to absorb calcium from food. When your vitamin D level drops, you absorb less calcium into your blood. Your body reacts fast to low blood calcium.

The parathyroid glands release more PTH to keep calcium in a normal range. PTH pulls calcium from your bones, increases calcium reabsorption in your kidneys, and helps activate more vitamin D. Older adults face higher risk because aging skin makes less vitamin D. If you avoid sunlight or always use strong sun protection, your levels may also fall.

Low vitamin D can exist for a long time without clear symptoms. You may feel tired or have bone or muscle pain, but many people notice nothing at first. A simple blood test can show low vitamin D and elevated PTH levels. When vitamin D improves, PTH levels often move back toward normal because your body no longer needs to raise calcium by breaking down bone.

3. Calcium Deficiencies

When your blood calcium level drops, your body reacts quickly. Your parathyroid glands release more parathyroid hormone to bring calcium back to a normal range. This response helps protect your muscles, nerves, and bones. You can develop low calcium for several reasons. You may not get enough calcium from your diet, especially if you avoid dairy or other calcium-rich foods.

Poor nutrition over time can slowly lower your calcium stores. Your body may also struggle to absorb calcium. Low vitamin D levels often play a role because vitamin D helps your gut absorb calcium from food. Digestive disorders that affect the intestines can reduce absorption as well.

Certain health conditions can also lower calcium levels. For example, kidney problems can disturb the balance of calcium and phosphorus in your blood, prompting your parathyroid glands to increase PTH production. When calcium stays low for a long time, your parathyroid glands may remain overactive. This ongoing stimulation keeps PTH levels higher than normal.

4. Adenoma

An adenoma is a noncancerous tumor that forms in one of your parathyroid glands. These glands sit in your neck near your thyroid. Even though an adenoma is benign, it can still cause problems. When an adenoma develops, it makes your gland release too much parathyroid hormone. This hormone controls the level of calcium in your blood and bones.

Extra PTH raises your blood calcium level, a condition called primary hyperparathyroidism. In most cases, a single adenoma affects just one gland. The other glands usually work normally. You may not notice symptoms at first. Many people learn they have high PTH after a routine blood test shows high calcium.

Over time, high calcium can lead to bone pain, weak bones, kidney stones, tiredness, or mood changes. Adenomas are more common as you age. Women develop them more often than men. In rare cases, radiation exposure to your head or neck or certain inherited conditions can increase your risk.

5. Genetics

Your genes can play a direct role in high parathyroid hormone levels. In some families, changes in certain genes cause the parathyroid glands to grow too much or form small tumors. These growths can make extra hormones and raise your blood calcium.

One example is familial isolated hyperparathyroidism. This inherited condition leads to overactive parathyroid glands. You may develop one or more benign tumors in these glands, which push your hormone levels higher than normal. Changes in specific genes can affect how your body controls calcium. For example:

• MEN1 gene changes can allow cells in the parathyroid glands to grow without normal control.
• CDC73 gene changes can also lead to gland growth and, in rare cases, cancer.
• CASR gene changes can make your body less sensitive to calcium levels in the blood.
• GCM2 gene changes may increase hormone production.

Most of these conditions follow an autosomal dominant pattern. This means you only need one changed copy of the gene from one parent to develop the disorder.

6. Kidney Stones

Kidney stones can both result from and signal high parathyroid hormone levels. When your parathyroid glands release too much hormone, your blood calcium level rises. Your kidneys then filter out the extra calcium into your urine. Over time, this extra calcium can form hard crystals.

These crystals can grow into stones inside your kidneys. Some stones stay small, but others grow large enough to block the flow of urine. You may feel sudden, sharp pain in your lower back or side if a stone moves into your urinary tract. The pain can spread to your lower abdomen or groin.

You might also notice nausea, vomiting, blood in your urine, or a strong urge to urinate. High parathyroid hormone often causes repeated kidney stones. This happens because the hormone pulls calcium from your bones into your blood, then into your urine. The more calcium in your urine, the higher your risk of stone formation.

7. Radiation Therapy

Radiation therapy to your head or neck can raise your risk of high parathyroid hormone. This treatment uses high-energy rays to kill cancer cells. It can also affect nearby healthy tissue, including your parathyroid glands. Your parathyroid glands sit behind your thyroid in your neck. When radiation reaches this area, it may damage the glands over time.

In some cases, the glands grow larger or become overactive. This change can cause them to release too much parathyroid hormone. High parathyroid hormone raises the level of calcium in your blood. You may not notice symptoms at first. Over time, you could develop bone pain, kidney stones, or feel tired and weak.

People who received radiation as children or young adults face a higher risk later in life. The problem may appear many years after treatment. If you had radiation therapy to your neck, your doctor may check your calcium and parathyroid hormone levels during routine blood tests.

8. Parathyroid Gland Damage

Damage to your parathyroid glands can cause your body to release too much parathyroid hormone. These four small glands sit behind your thyroid in your neck and control how much calcium stays in your blood. When one or more of these glands become injured, they may not work the right way.

In some cases, the damaged gland becomes overactive and releases excess PTH. This raises the level of calcium in your blood. Surgery in the neck area is a common cause of gland injury. Procedures involving the thyroid or nearby tissues can disturb the parathyroid glands. Even careful surgery can sometimes affect their blood supply or structure.

Physical trauma to your neck may damage the glands as well. Though less common, direct injury can disrupt normal hormone control. Damage does not always affect all four glands. Sometimes only one gland becomes overactive. Even one abnormal gland can raise your PTH level and shift your calcium balance.

9. Familial Hypocalciuric Hypercalcemia

Familial hypocalciuric hypercalcemia, or FHH, is a genetic condition that affects how your body senses calcium levels. It causes mild but long lasting high calcium in your blood. Because parathyroid hormone helps control calcium, your PTH level may appear normal or slightly high.

You inherit FHH in an autosomal dominant pattern. This means you only need one changed gene from a parent to have the condition. Changes most often affect the gene that controls the calcium sensing receptor, which helps your body decide how much PTH to release.

Unlike primary hyperparathyroidism, FHH usually causes low levels of calcium in your urine. Doctors often check a 24-hour urine calcium test to help tell the difference. In FHH, urine calcium is low even though blood calcium is high. Most people do not have symptoms, and you may learn about it after routine blood work shows high calcium.

10. Familial Isolated Hyperparathyroidism

Familial isolated hyperparathyroidism is a rare inherited disorder that causes your parathyroid glands to make too much hormone, which leads to high calcium in your blood. High calcium can cause kidney stones, nausea, vomiting, high blood pressure, bone thinning, weakness, and fatigue, though you may not notice symptoms at first.

This condition often runs in families and follows an autosomal dominant pattern, meaning you only need one changed gene from one parent to develop it. Several gene changes can cause it, including MEN1, CDC73, CASR, and sometimes GCM2. Most people develop a noncancerous growth called an adenoma in one of the four parathyroid glands.

Sometimes more than one gland becomes enlarged. Rarely, cancer develops in a gland, but this is uncommon. An overactive gland keeps releasing parathyroid hormone even when your calcium level is already high. This ongoing signal causes your bones to release more calcium into the blood.

11. Parathyroid Carcinoma

Parathyroid carcinoma is a rare cancer of one of your four parathyroid glands, which sit in your neck and control the calcium level in your blood. This cancer causes your gland to release very high amounts of parathyroid hormone (PTH), which raises your blood calcium to dangerous levels.

You may feel weak, tired, or confused, and some people develop kidney stones, bone pain, or frequent urination. Unlike common causes of high PTH, such as benign growth, this condition is cancer and affects men and women at similar rates. It may be suspected if you have very high calcium levels along with a lump in your neck. Imaging tests help locate the tumor, but doctors confirm the diagnosis after surgery.

A pathologist examines the removed tissue to check if cancer cells have spread into nearby tissue. Surgery is the main treatment, and the affected gland and sometimes nearby tissue are removed. If your calcium level becomes very high, you may need intravenous fluids, medications that lower calcium, or a calcimimetic drug to reduce PTH levels.

12. Chronic Kidney Disease

Chronic kidney disease develops when your kidneys slowly lose their ability to filter waste and balance minerals in your blood, often raising your parathyroid hormone levels. Your body increases PTH to try to correct changes in calcium and phosphorus.

Healthy kidneys help control vitamin D and remove extra phosphorus, but when your kidneys weaken, phosphorus builds up and your body may not activate enough vitamin D. It lowers calcium levels and signals your parathyroid glands to release more hormones.

Over time, this constant signal can cause the glands to become enlarged and overactive, a condition called secondary hyperparathyroidism. It is common in people with long-term kidney problems. As kidney disease worsens, you can develop bone pain, muscle weakness, or brittle bones because high parathyroid hormone pulls calcium from your bones. Chronic kidney disease often links to conditions such as diabetes and high blood pressure.

13. Malabsorption

Malabsorption happens when your body cannot absorb nutrients from food the right way, especially calcium or vitamin D. When this occurs, your parathyroid glands make more parathyroid hormone (PTH) to keep your blood calcium level in a safe range. Vitamin D helps your intestines absorb calcium. If you cannot absorb vitamin D well, your calcium level may drop and your parathyroid glands release more PTH to pull calcium from your bones.

Several conditions can cause malabsorption, including celiac disease, Crohn’s disease, chronic pancreatitis, and damage to the small intestine. Weight loss surgery can also reduce the area where calcium and vitamin D get absorbed. Long-term high PTH can weaken your bones if malabsorption continues. Over time, bone pain or fractures can occur because your body keeps taking calcium from your bones to correct low blood levels.

14. Clinical Testing and Workup

When your parathyroid hormone level is high, your doctor will start with simple blood tests to measure parathyroid hormone, calcium, phosphorus, and vitamin D. High calcium with high parathyroid hormone often points to primary hyperparathyroidism, while low or normal calcium may suggest a different cause. Your doctor may repeat the blood test to confirm the result, since lab errors can happen and levels can change during the day.

Kidney function tests are important because kidney disease can raise parathyroid hormone levels. Urine testing may follow, and a 24-hour urine collection checks how much calcium leaves your body. This helps distinguish between inherited conditions and true gland overactivity.

Imaging tests such as ultrasound or a special nuclear scan can show an enlarged gland or a benign growth and guide treatment planning. If bone loss is a concern, your doctor may order a bone density scan. In some cases, you may also need imaging of the kidneys to look for stones caused by high calcium levels.

15. Treatment

Your treatment depends on the cause of your high parathyroid hormone level. Your doctor will assess your blood calcium, kidney function, bone health, and symptoms to choose the best plan. If a benign growth makes one or more parathyroid glands overactive, a surgeon often removes the gland that produces too much hormone. This lowers your calcium level and protects your bones and kidneys.

If your calcium level is only slightly high and you have no symptoms, your doctor may suggest monitoring with regular blood tests, urine tests, and bone scans. You may also need to drink more fluids and stay active to support bone strength.

When low vitamin D causes high parathyroid hormone, treatment often includes vitamin D supplements. If kidney disease is the cause, your care may include active forms of vitamin D, phosphate binders, calcimimetic agents, or dialysis. Sometimes, surgery is necessary if hormone levels remain very high.