Hyperthyroidism causes high levels of thyroid hormones in the body. In some cases, people with high thyroid hormone levels may also have higher calcium levels.

Thyroid hormones can affect many processes in the body, including the regulation of calcium. Although they are not a main regulator of calcium, high thyroid hormone levels can cause elevated calcium levels.

Thyroid hormone levels may affect calcium levels by acting on how much calcium the bones store.

Read on to learn more about how hyperthyroidism affects calcium in the body.

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Calcium is an essential mineral for human functioning, and many different mechanisms in the body manage how much calcium is circulating in the blood or stored in the bones at any time. The three primary regulators of calcium in the body are vitamin D, calcitonin, and the parathyroid hormone.

The thyroid hormones — thyroid stimulating hormone, triiodothyronine, and thyroxine — also affect calcium in the body.

People with hyperthyroidism may have decreased bone mineral density. Low bone mineral density means fewer minerals, such as calcium, in the bones. This is a sign of reduced bone health, which can lead to fractures.

In people with low bone mineral density, the calcium missing from the bones ends up in the bloodstream. For people with hyperthyroidism, this means calcium levels in the blood may rise.

Conversely, people with hypothyroidism (low levels of thyroid hormones) may have low calcium levels.


In a 2018 study, researchers noted that participants with hypothyroidism had low calcium levels. The participants with hyperthyroidism had high calcium levels.

The researchers suggest that people with high levels of thyroid hormones experience increased bone turnover. This means that the bones release more calcium into the blood.

Despite this study and the mechanisms linking thyroid hormones and calcium levels in the blood, not everyone with a thyroid hormone imbalance has problems with calcium levels. For example, some research suggests that 15–20% of people with hyperthyroidism have high calcium levels.

The effects of thyroid diseases on calcium levels require further study.

A typical blood calcium range is between 8.5–10.5 milligrams per deciliter (mg/dL). Variations in the amount of calcium in the blood can be dangerous and, in some cases, life threatening.

Hypercalcemia occurs when a person has elevated blood calcium.

With mild hypercalcemia, the blood calcium level is about 10.6–11.5 mg/dL. As the calcium level rises above 11.5 mg/dL, symptoms may appear.

Experts divide conditions that cause hypercalcemia into two categories: non-parathyroid hormone-mediated (NPHM) causes and parathyroid-mediated causes.

The parathyroid hormone is a major hormone that regulates the amount of calcium in the blood. Causes of NPHM hypercalcemia can include the following:

Graves’ disease is a type of hyperthyroidism caused by the immune system.

The immune system produces an antibody that stimulates the thyroid gland to produce more thyroid-stimulating hormone. In people with Graves’ disease, the immune system attacks the thyroid gland, causing it to overproduce thyroid hormones.

At present, experts do not fully understand the link between elevated calcium levels and Graves’ disease.

A 2023 case study reported a rare situation in which a person developed Graves’ disease and high calcium. A doctor diagnosed Graves’ disease through an investigation of the person’s symptoms, blood tests, and physical exams.

However, there is little research on how many people with Graves’ disease have elevated calcium levels.

Hypercalcemia, which means abnormally high calcium levels, can be life threatening.

People with mild hypercalcemia may not have any symptoms. However, when the calcium level in the blood rises above 11.5 mg/dL, people may experience nonspecific symptoms, including:

Doctors treating hypercalcemia may detect other symptoms, such as high blood pressure, slow heart rate, and hyperactive reflexes. Coma can occur in people with severe hypercalcemia.

People with symptoms of hypercalcemia should contact a doctor. When treating a change in blood calcium, the doctor will search for the underlying cause.

Symptoms of thyroid hormone or calcium imbalance can be nonspecific. Talking with a doctor about symptoms can help determine the cause. Blood tests can highlight changes in hormones or minerals that can help a doctor make a diagnosis.

Changes in thyroid hormone levels may affect calcium levels in the blood. Some people with hyperthyroidism have high levels of calcium in their blood.

However, changes in blood calcium levels do not happen in everyone with a thyroid hormone imbalance.

High blood calcium can be dangerous. Removing calcium from the body may help ease symptoms. However, a doctor must find and treat the underlying cause.