Parathyroid Diseases: The Tiny Glands Behind Your Calcium Levels

By Prof. Dr. Zahid Mahmood — General, Laparoscopic & Laser Surgeon, Lahore

Most people have never heard of their parathyroid glands, and that’s understandable — they are four tiny structures, each about the size of a grain of rice, tucked behind the thyroid in the neck. Yet these small glands control something fundamental: the level of calcium in your blood. When they malfunction, the effects can be silent for years, or they can show up as kidney stones, weak bones, or a range of vague symptoms that are easy to dismiss. This article explains what the parathyroid glands do, the conditions that affect them, and when surgery becomes the answer.

What the parathyroid glands actually do

Despite the name, the parathyroid glands have nothing to do with the thyroid’s job of controlling metabolism. Their only role is regulating calcium. They do this by producing parathyroid hormone (PTH), which is released whenever blood calcium drops too low. PTH then acts on three places at once: it pulls calcium out of bone, tells the kidneys to hold on to more calcium, and — indirectly, through activating vitamin D — increases how much calcium the gut absorbs from food. The result is a tightly controlled feedback loop that keeps blood calcium within a narrow, healthy range at all times.

Most people have four parathyroid glands, though a meaningful minority have extra ones, and their exact position can vary — which is one reason parathyroid surgery requires real anatomical expertise.

Primary hyperparathyroidism — the most common parathyroid disease

The condition I see most often is primary hyperparathyroidism, where one or more of the glands become overactive on their own and produce too much PTH regardless of what the body actually needs. In the great majority of cases, this is caused by a single benign adenoma — a small, benign overgrowth of one gland — rather than a problem affecting all four.

Classic teaching described this disease by the memorable phrase “bones, stones, abdominal groans, and psychiatric overtones” — referring to bone pain and fractures, kidney stones, abdominal symptoms like pancreatitis or peptic ulcers, and mood or memory changes. Today, this severe presentation is much less common. Because calcium is now checked routinely on ordinary blood tests, most patients are diagnosed incidentally, often with no symptoms at all, or only vague ones — tiredness, mild low mood, muscle weakness, or difficulty concentrating that patients rarely connect to a calcium problem.

Even without dramatic symptoms, the disease is not harmless if left untreated. Kidney stones remain the most common clinical problem, affecting around 15–20% of patients, and many more have excess calcium in their urine that raises stone risk. Bone density can also decline over time — this disease tends to particularly affect the outer, harder shell of bone (as opposed to the spongier bone inside), which is why we specifically check the forearm bone on a bone density scan, not just the spine and hip as in routine osteoporosis screening.

How we diagnose it

Primary hyperparathyroidism is a blood diagnosis, not something you can feel or see. The pattern that confirms it is a raised calcium level occurring alongside a PTH level that is inappropriately high — in a healthy person, high calcium should switch PTH production off, so a PTH level that stays high or normal in the presence of high calcium is the tell-tale sign. We also check phosphate (usually low in this condition), kidney function, and vitamin D, and often collect a 24-hour urine sample to rule out a rare, harmless hereditary look-alike condition that does not need surgery at all.

Once the diagnosis is confirmed on blood tests, imaging is used only to help plan surgery — it is never used to make the diagnosis itself, and a “normal” scan does not rule the condition out. The two most useful tests are a sestamibi scan, a nuclear medicine scan that lights up the overactive gland, and a focused ultrasound of the neck. When these two tests agree on the location of the problem gland, it lets us plan a smaller, more targeted operation.

Should every patient with high calcium have surgery?

Not necessarily — but the bar for recommending surgery is lower than many patients expect. Any patient with actual symptoms should be offered surgery. For patients found incidentally with no obvious symptoms, international guidelines recommend surgery when any of the following are present: calcium significantly above the normal range, reduced kidney function or a high risk of kidney stones, evidence of bone thinning on a bone density scan (or a previous fracture from weak bone), or age under 50 — because younger patients face many more years of exposure to the condition’s slow damage if left untreated. In practice, most patients who meet these criteria feel notably better after surgery, even those who did not think they had symptoms beforehand.

How the surgery is done

When imaging clearly identifies a single overactive gland, we can typically perform a minimally invasive parathyroidectomy — removing just that one gland through a small incision, often under an hour, with patients going home the same or next day. During the operation, we can check a PTH blood level in real time: because PTH clears from the bloodstream within minutes, a sharp drop after removing the gland confirms the correct gland has been taken out and the problem is solved.

When imaging does not clearly localise the problem, or when the family history or genetics suggest that more than one gland may be involved, a more traditional exploration of all four glands is performed instead, through a single incision along a natural neck crease. In this situation, three and a half glands are typically removed, leaving a small remnant of healthy tissue behind — enough to maintain normal calcium regulation without the disease recurring in that one small piece.

Modern parathyroid surgery is very safe, with a cure rate above 95% in experienced hands. The two risks I always discuss with patients beforehand are: injury to the nerve that controls the voice box, which is uncommon (well under 1%), and low calcium after surgery — usually a temporary dip needing calcium and vitamin D tablets for a few weeks, with permanently low calcium requiring lifelong supplementation being rare (around 1 in 200 cases).

A hypercalcaemic crisis — a genuine emergency

Occasionally, calcium rises to a dangerously high level — this is called a hypercalcaemic crisis and needs urgent hospital treatment. It causes confusion, abdominal pain, vomiting, and severe dehydration, and at very high levels it can affect the heart rhythm. Treatment centres on aggressive intravenous fluids to flush calcium out through the kidneys, sometimes combined with specific medications to reduce calcium release from bone. This is uncommon but is one of the reasons unexplained high calcium should never be ignored once identified on a blood test.

Secondary hyperparathyroidism — a different problem, usually from kidney disease

Not every case of overactive parathyroid glands starts in the glands themselves. In secondary hyperparathyroidism, the parathyroid glands are working overtime in response to a problem elsewhere — almost always chronic kidney disease. Failing kidneys struggle to clear phosphate and activate vitamin D properly, and the body’s calcium-sensing system reacts by pushing PTH higher and higher to compensate. Over time, all four glands can enlarge.

The pattern on blood tests looks different from primary disease: calcium is typically normal or even low, phosphate is high, vitamin D is low, and PTH is elevated. Because this is a whole-body problem rather than a localised gland problem, imaging is not usually needed to make treatment decisions. First-line management is medical — vitamin D and calcium replacement, medications that bind excess phosphate, and drugs called calcimimetics that reduce PTH secretion directly. Surgery is reserved for patients whose disease becomes severe or resistant to medication despite these measures, particularly those with worsening bone pain, progressive calcium deposits in soft tissue, or a rare but serious complication called calciphylaxis, where calcium deposits in small blood vessels cause painful skin ulceration — this needs urgent parathyroid surgery, which can be genuinely life-saving in that setting.

Tertiary hyperparathyroidism — after a kidney transplant

Sometimes, after a successful kidney transplant restores normal kidney function, one or more parathyroid glands that enlarged during years of kidney disease continue behaving independently, continuing to overproduce PTH even though the original trigger is gone. This is called tertiary hyperparathyroidism. Very few of these patients ultimately need surgery, but when calcium remains persistently high a year or more after transplant, or when one gland shows nodular change on ultrasound, surgical removal of the overactive tissue is the definitive treatment.

Parathyroid cancer — genuinely rare

I want to reassure readers on this point directly: parathyroid cancer is extremely rare, accounting for roughly 1 in 100 cases of primary hyperparathyroidism. It tends to cause more dramatic blood test abnormalities — a much higher calcium and PTH than typical benign disease — and, unlike benign disease, can sometimes be felt as a lump in the neck. Treatment is surgical removal, performed carefully to avoid any spillage of tumour tissue, and outcomes are generally favourable when the cancer is fully removed at the first operation.

Warning signs worth getting checked

Kidney stones, especially recurrent ones
Unexplained fatigue, low mood, or difficulty concentrating that doesn’t have another clear cause
Bone pain or a fracture from a minor injury
A high calcium result on a routine blood test — even without symptoms
Long-standing kidney disease with worsening bone pain or itching
Any lump felt in the neck alongside abnormal calcium results

What you should do

If a blood test has ever shown a raised calcium level, don’t let it be dismissed as an incidental finding — ask for it to be properly investigated with a PTH level. Most people with primary hyperparathyroidism feel measurably better after a short, safe operation, even when they didn’t realise how much the condition had been affecting them. And if you have chronic kidney disease, regular monitoring of calcium, phosphate, and PTH should be part of your routine care, since catching secondary hyperparathyroidism early makes it far easier to manage.

To book a consultation with Prof. Dr. Zahid Mahmood, call 0300 413 0159 or visit professorzahid.com.

This article is for general awareness and does not replace a personal medical consultation.

Parathyroid Diseases: The Tiny Glands Behind Your Calcium Levels

Parathyroid Diseases: The Tiny Glands Behind Your Calcium Levels

What the parathyroid glands actually do

Primary hyperparathyroidism — the most common parathyroid disease

How we diagnose it

Should every patient with high calcium have surgery?

How the surgery is done

A hypercalcaemic crisis — a genuine emergency

Secondary hyperparathyroidism — a different problem, usually from kidney disease

Tertiary hyperparathyroidism — after a kidney transplant

Parathyroid cancer — genuinely rare

Warning signs worth getting checked

What you should do

Related articles

Other conditions we treat

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