Some people with hyperparathyroidism may notice weight gain or weight loss. These changes may occur due to factors like underlying medical conditions or appetite changes.

Hyperparathyroidism is characterized by high levels of parathyroid hormone. This hormone plays an important role in regulating levels of calcium and phosphorus in your blood. When calcium levels drop, your body produces more of this hormone to release more calcium into your blood.

Having high levels of parathyroid hormone might indirectly lead to weight changes in several ways. For example, some people may develop nausea and have trouble eating. Reduced food intake may cause weight loss.

In reverse, some people with very high levels of parathyroid hormone may develop fatigue and reduce their level of physical activity. Reduced activity might cause weight gain.

Read more about the connection between parathyroid hormone and weight changes.

Hyperparathyroidism is primarily divided into three categories:

  • Primary hyperparathyroidism: When the problem originates in your parathyroid gland. The cause is usually a non-cancerous tumor.
  • Secondary hyperparathyroidism: When another condition, like kidney failure, lowers calcium levels in your blood and causes your body to produce extra parathyroid hormone in response.
  • Tertiary hyperparathyroidism: When long-term secondary hyperparathyroidism begins to act like primary.

Both primary and secondary hyperparathyroidism may be associated with weight loss for some people. Here are some of the specific reasons why.

Nausea and vomiting

Nausea and vomiting are potential symptoms of primary hyperparathyroidism. Experiencing these symptoms may cause you to eat less. Reducing food intake may lead to unintentional weight loss.

Leptin changes

Leptin is a hormone primarily secreted by fat cells that makes you feel full. It’s thought that increased levels of leptin resistance in people with obesity may exacerbate secondary hyperparathyroidism.

Associated conditions like kidney failure

Secondary hyperparathyroidism is commonly caused by kidney failure. Loss of appetite is common in people with kidney failure. Reduced appetite generally leads to a lower calorie intake and weight loss.

Muscle wasting is also common in people with kidney failure. Muscle wasting is the loss of muscle mass and strength.

Changes to fat tissue

Most of the fat in your body is classified as white fat. Your body uses white fat as an energy reserve. Brown fat is another type of fat that helps you create heat and maintain your body temperature.

Some evidence suggests that parathyroid hormone may stimulate the conversion of white fat tissue to brown fat. This change may trigger:

  • increased energy expenditure
  • loss of muscle and fat
  • weight loss

Most people with hyperparathyroidism seem to have increased body weight due to greater insulin resistance and reduced breakdown of fat tissue. Insulin resistance is when your body no longer responds to the hormone insulin. It’s the characteristic feature of type 2 diabetes.

It’s important to point out that the two conditions might frequently occur together, but one doesn’t necessarily cause the other. High body weight has been described as a risk factor for hyperparathyroidism.

Additionally, fatigue is a potential complication of hyperparathyroidism. Fatigue may lead to reduced physical activity in some people, and reduced activity may lead to weight gain.

Excess calcium may interfere with fat breakdown

It’s been suggested that excess levels of calcium in the blood in people with hyperparathyroidism may interfere with the breakdown of fat in response to a group of hormones called catecholamines. These hormones include norepinephrine and epinephrine. Normally, these hormones are released into your blood during times of stress to make energy more readily available.

If you have hyperparathyroidism, you don’t need to follow any particular diet. It’s a good idea to eat a balanced diet filled with plenty of nutrient-dense and minimally processed foods. For example, the Mediterranean diet is a dietary pattern that’s consistently associated with good health outcomes.

You may need to take a vitamin D supplement if you’re low in vitamin D. Your healthcare professional can advise you on how much you may need to take.

If you have an underlying condition like kidney failure, you may need to make additional dietary changes. For example, you may benefit from reducing salt intake.

Most people with hyperparathyroidism have no noticeable symptoms. When symptoms do appear, symptoms may include:

  • aches and pains in bones and joints
  • muscle weakness
  • fatigue
  • depression

People with more severe disease may have:

It’s important to seek medical attention if you develop potential symptoms of hyperparathyroidism without a known cause. Most of the symptoms of hyperparathyroidism are general and require a proper medical evaluation to find the underlying cause.

It’s especially important to see a doctor if you suspect you may have kidney failure. Early symptoms of kidney failure can include:

  • fatigue
  • swelling in your feet and legs
  • shortness of breath

Some people with hyperparathyroidism may notice either an increase or a decrease in their weight. Symptoms like fatigue may lead to reduced physical activity and weight gain. Loss of appetite may lead to reduced food intake and weight loss.

Weight gain or loss can have many causes other than hyperparathyroidism. Sometimes, underlying conditions that can cause hyperparathyroidism are the cause. For example, people with kidney failure commonly develop muscle wasting, which may lead to weight loss.