Primary hyperparathyroidism is a hormonal disorder where one or more of the tiny parathyroid glands in your neck become overactive and produce too much parathyroid hormone, causing calcium levels in your blood to rise beyond normal ranges. While many people have no symptoms and discover the condition through routine blood tests, others may experience bone weakening, kidney stones, or various physical and emotional changes that can affect their daily lives.

How Common Is Primary Hyperparathyroidism

Primary hyperparathyroidism stands as one of the most frequently diagnosed hormonal disorders affecting people today. In the United States alone, approximately 100,000 individuals develop this condition each year. The prevalence ranges from about one to seven cases per 1,000 adults in the general population, making it a significant health concern that healthcare providers encounter regularly.^[1][3]

The condition does not affect everyone equally. Women face a considerably higher risk than men, being about two to three times more likely to develop primary hyperparathyroidism. This gender difference becomes particularly pronounced after menopause, when many women are first diagnosed during routine health screenings. The condition also shows a preference for certain age groups, becoming increasingly common as people grow older. Most diagnoses occur in people over the age of 50, with the average age at diagnosis being around 55 years.^[4][13]

Interestingly, primary hyperparathyroidism appears more frequently in the African-American population compared to other ethnic groups. The risk of developing this condition increases steadily with advancing age, particularly affecting those over 65 years old. In this older age group, the estimated incidence reaches approximately one case per 1,000 men and two to three cases per 1,000 women each year.^[3][4]

What Causes Primary Hyperparathyroidism

Understanding what causes primary hyperparathyroidism begins with recognizing that something has gone wrong with the parathyroid glands themselves. These four pea-sized glands, located behind the thyroid gland in your neck, have a single important job: producing parathyroid hormone (PTH), which is the chemical messenger that helps keep calcium levels balanced in your blood and bones.^[1]

In the vast majority of cases—about 85 percent—the culprit is a single adenoma, which is a noncancerous growth or tumor that develops on one of the parathyroid glands. This adenoma causes that particular gland to become overactive, producing far more parathyroid hormone than the body needs. The gland essentially loses its ability to respond to normal signals that would tell it to stop making the hormone.^[4][5]

Less commonly, the condition results from hyperplasia, a situation where all four parathyroid glands become enlarged and overactive simultaneously. Multiple adenomas affecting more than one gland can also occur, though this is relatively rare. Together, these situations account for most of the remaining cases not caused by a single adenoma.^[5]

Parathyroid cancer is an extremely rare cause of primary hyperparathyroidism, responsible for fewer than 0.5 percent of cases. When it does occur, however, it requires different treatment approaches than benign causes.^[4]

Some people develop primary hyperparathyroidism because of specific circumstances in their lives or medical histories. Past exposure to radiation in the neck area, even many years earlier, can increase the risk. Certain medications, particularly lithium (often used to treat mood disorders) and thiazide diuretics (used for high blood pressure), have been linked to overactive parathyroid glands. In some cases, the excess activity persists even after stopping these medications.^[3][4]

A small percentage of cases—between 10 and 20 percent—run in families. People may inherit genes that predispose them to developing primary hyperparathyroidism, sometimes as part of broader genetic syndromes such as Multiple Endocrine Neoplasia Type 1 (MEN1), Multiple Endocrine Neoplasia Type 2A (MEN2A), or familial hyperparathyroidism.^[4][5]

Risk Factors for Developing Primary Hyperparathyroidism

Certain groups of people face elevated chances of developing primary hyperparathyroidism due to various factors. Postmenopausal women represent the largest at-risk group, combining both the female gender predisposition and the age-related increase in occurrence. The hormonal changes that happen during and after menopause may play a role, though the exact mechanism remains under investigation.^[4]

Age itself serves as an important risk factor regardless of gender. As people move beyond their 50s and into their 60s, 70s, and beyond, their likelihood of developing primary hyperparathyroidism climbs steadily. This age-related increase means that older adults should be particularly aware of the condition during routine health checkups.^[3]

Anyone who has received radiation therapy to the neck area in the past faces an elevated risk. This includes people who were treated for cancers of the head, neck, or thyroid, even if the radiation occurred decades ago. The risk can persist for many years following the treatment.^[4]

People taking lithium for psychiatric conditions such as bipolar disorder should be aware of this potential side effect. Similarly, those on long-term thiazide diuretics for blood pressure control may have an increased risk. If you take either of these medications, it does not mean you will definitely develop primary hyperparathyroidism, but your doctor may want to monitor your calcium levels more closely.^[3]

Family history matters significantly. If you have blood relatives who have been diagnosed with primary hyperparathyroidism or related genetic syndromes like Multiple Endocrine Neoplasia, your own risk increases. Genetic counseling may be helpful for families with multiple affected members to understand inheritance patterns and testing options.^[5]

Recognizing the Symptoms of Primary Hyperparathyroidism

Many people with primary hyperparathyroidism experience no noticeable symptoms at all. The condition often comes as a complete surprise when elevated calcium levels appear on routine blood work ordered for other reasons. Since the widespread introduction of automated blood chemistry screening in the 1970s, doctors have been able to detect the condition before it causes obvious problems. Today, approximately 80 percent of cases are discovered this way, in people who feel perfectly fine.^[15]

When symptoms do occur, they relate to the elevated calcium levels in the blood, a condition called hypercalcemia. Medical professionals sometimes summarize the classic symptoms with a memorable phrase: “stones, bones, abdominal groans, thrones and psychiatric overtones.” Each part of this saying points to different body systems affected by too much calcium.^[5]

“Stones” refers to kidney-related problems. Excess calcium can form kidney stones, which are small, hard clumps of calcium that cause severe pain when they move through the urinary system. Some people develop a condition called nephrocalcinosis, where calcium deposits build up in the kidney tissue itself. Over time, these calcium-related kidney problems can progress to affect how well the kidneys filter waste from the blood, potentially leading to kidney damage. People may also experience excessive thirst and urinate more frequently than usual, sometimes developing a form of diabetes insipidus, which causes the body to produce large amounts of dilute urine.^[5]

“Bones” describes the skeletal complications that can develop. The classic bone disease associated with primary hyperparathyroidism is called osteitis fibrosa cystica, though this severe manifestation is quite rare today. More commonly, people experience bone pain and may suffer from osteoporosis, where bones become thin and brittle, increasing the risk of fractures even from minor falls or injuries. Joint pain and general aches can also occur. Some people notice these bone-related symptoms before any diagnosis is made.^[5]

“Abdominal groans” captures the digestive system symptoms. These include constipation, indigestion, nausea, and vomiting. High calcium levels can trigger increased production of stomach acid, potentially leading to peptic ulcers that cause stomach pain. In more severe cases, excess calcium can cause inflammation of the pancreas, a serious condition called acute pancreatitis.^[5]

“Thrones” is a somewhat delicate reference to spending more time in the bathroom due to increased urination and constipation, both common complaints when calcium levels are elevated.^[5]

“Psychiatric overtones” acknowledges the effects on mental and emotional wellbeing. Many people with primary hyperparathyroidism experience fatigue that makes them feel tired much of the time. Muscle weakness can make everyday activities more difficult. Mood changes are common, including depression, anxiety, and irritability. Some people have trouble concentrating or experience memory problems. In severe cases, confusion, delirium, or even coma can occur, though these extreme manifestations are rare with modern early detection.^[5][7]

Other symptoms that people may experience include general weakness, loss of appetite, itching of the skin, and band-shaped cloudy areas on the cornea of the eye called band keratopathy. Some people notice that they develop high blood pressure or that their existing blood pressure becomes harder to control.^[5]

How Primary Hyperparathyroidism Affects Your Body

To understand what goes wrong in primary hyperparathyroidism, it helps to know how the parathyroid glands normally work. These four tiny glands have one specialized function: making parathyroid hormone in response to calcium levels in your blood. When calcium dips too low, the glands release more hormone. When calcium returns to normal, hormone production decreases. This constant adjustment happens throughout the day, keeping calcium in a narrow, healthy range.^[4]

Parathyroid hormone raises calcium levels through three main actions. First, it signals bones to release calcium stored in the bone tissue into the bloodstream. Bones serve as the body’s calcium warehouse, containing most of the calcium in your body. Second, the hormone tells the kidneys to hold onto calcium instead of letting it leave the body in urine. Third, it instructs the kidneys to convert vitamin D into its active form, which then signals the intestines to absorb more calcium from food you eat.^[1][4]

Calcium plays critical roles throughout the body. Nerves need calcium to transmit signals properly. Muscles require calcium to contract and relax, including the heart muscle that pumps blood. Blood vessels use calcium to maintain proper tone. The blood clotting system depends on calcium. Bones and teeth obviously need calcium for their structure and strength. Maintaining the right calcium level is so important that the body has multiple backup systems to keep it balanced.^[1]

In primary hyperparathyroidism, one or more parathyroid glands loses the ability to properly sense calcium levels and regulate hormone production. The affected gland or glands produce too much parathyroid hormone continuously, regardless of whether calcium is already at healthy levels. This excess hormone keeps pulling calcium from the bones, preventing the kidneys from eliminating calcium, and driving up calcium absorption from food—all at once.^[1]

The result is that calcium levels in the blood climb above the normal range. Initially, this might cause no problems at all. But over months and years, the continuous drain of calcium from bones weakens the skeletal structure. Bones become less dense and more fragile, a process that can lead to osteoporosis and an increased risk of fractures. Meanwhile, the excess calcium circulating in the blood and being filtered by the kidneys can crystallize, forming kidney stones or depositing in the kidney tissue itself, potentially damaging kidney function over time.^[3]

High blood calcium affects how cells throughout the body function. It can slow down the digestive system, causing constipation. It can interfere with normal kidney function, leading to excessive urination and thirst. The nervous system and brain can be affected, contributing to the fatigue, mood changes, and cognitive difficulties that some people experience. When calcium levels become very high, it can even affect heart rhythm and blood pressure.^[5]

Preventing Primary Hyperparathyroidism

Unfortunately, there is no known way to prevent primary hyperparathyroidism from developing, because in most cases the underlying cause—such as a parathyroid adenoma—occurs spontaneously without any identifiable triggering factor. The condition is not caused by anything people do or fail to do in their daily lives, such as diet choices or lifestyle habits.^[1]

However, being aware of your risk factors can help with early detection. If you fall into a higher-risk category—for example, if you are a postmenopausal woman, have a family history of parathyroid problems, take lithium or thiazide diuretics, or received neck radiation in the past—make sure your healthcare provider knows. Regular checkups that include blood work can catch elevated calcium levels early, before complications develop.^[3]

For people with genetic syndromes that include primary hyperparathyroidism as a feature, such as Multiple Endocrine Neoplasia, genetic counseling and regular monitoring can help detect the condition early. Family members of affected individuals may benefit from genetic testing to determine their own risk.^[5]

Early detection represents the most important approach to minimizing complications. Since the 1970s, when automated blood chemistry panels became routine, doctors have been able to identify primary hyperparathyroidism before it causes serious bone disease, kidney stones, or other major complications. Most people today are diagnosed at an asymptomatic or mildly symptomatic stage, when treatment options are most effective and outcomes are best.^[15]