Hyperparathyroidism Explained

Hyperparathyroidism is a condition in which one or more of the parathyroid glands make too much parathyroid hormone. Because this hormone controls calcium, the result is often a raised blood calcium level, which can affect the bones, kidneys, and other systems. It is usually identified through blood tests that measure calcium and parathyroid hormone together.

What hyperparathyroidism is

The four parathyroid glands are small glands in the neck, usually sitting just behind the thyroid. Despite their location, they have nothing to do with thyroid hormone; their job is to manage calcium. They release parathyroid hormone (PTH), which keeps blood calcium in a tight range by acting in three ways: it draws calcium out of the bones, prompts the kidneys to hold on to calcium, and helps activate vitamin D so the gut absorbs more calcium from food. When the glands make too much PTH, these effects combine to push blood calcium upward.

The condition is divided into forms that behave quite differently. In the primary form, the problem lies in the parathyroid glands themselves — often a single benign growth — and calcium is typically high. In the secondary form, the glands are healthy but are responding to a problem elsewhere, commonly low vitamin D or long-term kidney disease, that lowers calcium; PTH rises to compensate. A tertiary form can follow long-standing secondary disease, when the glands become persistently overactive on their own. Distinguishing these is an important part of the evaluation, because the causes and management differ.

Common signs and symptoms

Many people with mild primary hyperparathyroidism have no symptoms at all, and it is found on a routine blood test that happens to include calcium. When symptoms do occur, they often reflect a raised calcium level and may include:

• Tiredness and weakness
• Increased thirst and frequent urination
• Kidney stones, or blood or grit in the urine
• Bone aches or fragility, and fractures over time
• Constipation, nausea, indigestion, or loss of appetite
• Low mood, irritability, or difficulty concentrating
• Aching muscles and joints

An old description of the more advanced picture grouped these into bones, stones, abdominal moans, and mood changes. In practice, modern blood testing usually catches the condition long before such a full set of symptoms appears.

What causes it

Primary hyperparathyroidism is most often caused by a single benign growth on one parathyroid gland, called an adenoma. Less commonly, several glands are enlarged and overactive together, a pattern called hyperplasia, and rarely a parathyroid cancer is responsible. Secondary hyperparathyroidism arises when something outside the glands lowers calcium or vitamin D and prompts the glands to release more PTH; chronic kidney disease and vitamin D deficiency are the common reasons, and poor calcium absorption can contribute. A small number of cases relate to inherited conditions in which parathyroid overactivity runs in families, which is why a clinician may ask about family history and, occasionally, about other glands.

How it is diagnosed

Diagnosis rests on interpreting calcium and parathyroid hormone together, because the relationship between the two reveals what the glands are doing. A high calcium with a high or even middle-of-the-range PTH is suspicious, because in a healthy person a high calcium should switch PTH off. Common tests include:

• Blood calcium — often raised in primary hyperparathyroidism; sometimes adjusted for the level of the protein albumin.
• Parathyroid hormone (PTH) — high, or inappropriately normal relative to a raised calcium.
• Vitamin D — to check for deficiency, which can drive the secondary form and influence interpretation.
• Kidney function tests — since kidney disease is a common cause of the secondary form.
• Phosphate — which often moves in the opposite direction to calcium in these conditions.
• Urine calcium — used in some situations to clarify the picture and to distinguish look-alike conditions.

If surgery is being considered, imaging may be used to locate an overactive gland, and a bone density scan may assess the effect on the skeleton. The table below sketches the typical patterns; it is illustrative only, units and ranges vary by laboratory, and a clinician interprets the whole picture together.

For background on the markers themselves, see our blood tests and hormones sections, and our conditions overview for related topics.

How it is generally managed

Management depends on the form, the calcium level, and the effect on bones and kidneys, and it is decided with a clinician; this page does not describe medicines or doses. In primary disease, surgery to remove an overactive gland is a common approach, while milder cases without complications may be monitored over time with periodic blood tests and bone checks. In secondary disease, the focus is on addressing the underlying cause — such as correcting vitamin D deficiency or managing kidney disease. Staying well hydrated is often discussed, and a clinician may review medicines or supplements that affect calcium. General treatment principles are outlined in our treatments section, and our symptoms overview can help you describe what you are experiencing.

Complications and when to seek care

Untreated, a high calcium can over time contribute to kidney stones, reduced kidney function, and weaker bones that are more prone to fracture. A markedly high calcium can cause confusion, severe weakness, vomiting, or a disturbed heart rhythm and needs urgent medical attention. Sudden severe symptoms, signs of a kidney stone, or new confusion in someone known to have a high calcium are reasons to seek prompt care rather than waiting for a routine appointment.

Living with hyperparathyroidism

For people whose mild disease is monitored rather than treated, follow-up usually involves periodic checks of calcium, kidney function, and bone density to make sure nothing is progressing. Many people find it helpful to keep an up-to-date list of medicines and supplements, since some calcium and vitamin D products affect the picture, and to discuss them with a clinician rather than adjusting them alone. When surgery successfully removes an overactive gland, calcium often returns to normal, though follow-up continues to confirm the result and watch the bones.