- 01Two results make the diagnosis, not one
Primary hyperparathyroidism is a high calcium together with a PTH that did not switch off. Either number alone is inconclusive; the pairing is the whole call.
A high calcium on a blood test rarely means what people fear. In outpatients, the most common reason is primary hyperparathyroidism: one of the four small parathyroid glands in your neck is overproducing parathyroid hormone (PTH), the hormone that raises blood calcium, partly by drawing it out of your bones. What clinches it is the pairing, a high calcium sitting next to a PTH that has not switched off.
The pairing that makes the diagnosis
Your parathyroid glands are four grain-sized glands behind the thyroid in your neck. As our PTH marker page puts it, they "work like a thermostat for blood calcium: when calcium falls they release PTH to raise it, and when calcium rises they switch PTH off." A high calcium paired with a PTH that stayed on breaks that rule, and the broken rule is the diagnosis. 1 A high PTH on its own means little until you see the calcium sitting next to it.
When blood calcium and PTH are both clearly raised at the same time, primary hyperparathyroidism is by far the most likely explanation.Summarizing the Fifth International Workshop on Primary Hyperparathyroidism, 2022
How to read calcium and PTH together
In people seen as outpatients, primary hyperparathyroidism is the single most common reason for a high calcium, and about 80 to 85% of the time it comes from a single benign gland, an adenoma, rather than cancer. 3 In people who are hospitalized or seriously ill, cancer becomes the more likely cause, which is why a genuinely high calcium is never brushed off. 3
What is hyperparathyroidism?
Hyperparathyroidism means the parathyroid glands are making too much PTH, and it comes in two forms that are close to opposites. In primary hyperparathyroidism, a gland overproduces on its own and blood calcium climbs. In secondary hyperparathyroidism, PTH is high for a reason: the glands are working overtime to correct a low calcium, low vitamin D, or the mineral problems of chronic kidney disease, and calcium stays low or normal. A high PTH is not automatically a parathyroid tumor. 5
What are the symptoms of hyperparathyroidism?
Most people with primary hyperparathyroidism today feel nothing; it is found by chance when a calcium test comes back high for another reason. 4 It most often affects women, and is most common after menopause. 3 When symptoms do appear, the classic shorthand is 'stones, bones, groans, and moans':
- Kidney stones (the 'stones'), from calcium building up in the urine
- Bone thinning and fractures (the 'bones'), as the extra PTH draws calcium out of the skeleton
- Stomach aches, constipation, nausea, and sometimes ulcers or pancreatitis (the 'groans')
- Low mood, fatigue, poor concentration, and trouble sleeping (the 'moans')
- Frequent thirst and urination, from calcium spilling into the urine
How is it diagnosed?
Diagnosis starts with the two numbers read side by side: total blood calcium and intact PTH (the standard PTH blood test), ideally from a fasting morning draw. Because low vitamin D can raise PTH on its own, a 25-hydroxyvitamin D level is measured so a high PTH is not mistaken for a parathyroid problem when it is really the body correcting a vitamin D shortfall. When the picture is unclear, a 24-hour urine calcium helps separate primary hyperparathyroidism from familial hypocalciuric hypercalcemia (FHH), a benign inherited condition that raises calcium but spills very little of it into the urine. 15 Disease before age 40, or several affected relatives, can point to an inherited syndrome such as MEN1 and prompts screening of family members. 3
| Result | Typical adult range | What flags concern |
|---|---|---|
| Total blood calcium | 8.5-10.2 mg/dL (varies by lab) | Above the range is hypercalcemia (high blood calcium); correct for albumin first |
| Ionized calcium | 4.6-5.3 mg/dL | The active fraction; used when albumin is abnormal or the total is borderline |
| Intact PTH | 15-65 pg/mL | Not suppressed when calcium is high is the red flag, even a mid-range value |
| 25-OH vitamin D | 30 ng/mL or above = sufficient | Low vitamin D raises PTH by itself, so it is checked before blaming the glands |
Reference ranges differ slightly between labs, so read your own result against the range printed on your report. What does not change is the logic: a PTH that stays up while calcium is high is the abnormal combination. 1
Where an example calcium fallsmg/dL
When is surgery considered?
Removing the overactive gland (an operation called parathyroidectomy) is the only definitive cure. 2 Plenty of people with mild, symptom-free disease are watched instead, with periodic calcium, kidney-function, and bone-density checks. Guideline criteria that tip the decision toward surgery include: 1
- Age under 50
- Blood calcium more than 1 mg/dL above the top of the normal range
- A bone-density T-score of -2.5 or lower (a standard score for thinning bone), or a fragility fracture
- An eGFR (kidney filtration estimate) below 60 mL/min/1.73m2, kidney stones, or a high 24-hour urine calcium
The skeleton is the organ that pays. Sustained high PTH draws calcium out of bone, thinning the hard outer (cortical) bone first and raising the risk of osteoporosis and fractures. That is why a bone-density scan is part of the workup, and why bone loss is one of the reasons to operate. As our bone-markers explainer puts it, "bone is living tissue that is constantly broken down and rebuilt, and turnover markers that run high can mean it is being lost faster than it is replaced."
Citations
- Bilezikian JP et al. Evaluation and Management of Primary Hyperparathyroidism: Summary Statement and Guidelines from the Fifth International Workshop. J Bone Miner Res 2022;37(11):2293-2314
- Wilhelm SM et al. The American Association of Endocrine Surgeons Guidelines for Definitive Management of Primary Hyperparathyroidism. JAMA Surgery 2016;151(10):959-968
- Bilezikian JP, Bandeira L, Khan A, Cusano NE. Hyperparathyroidism. Lancet 2018;391(10116):168-178
- NIDDK. Primary Hyperparathyroidism (health information)
- Fraser WD. Hyperparathyroidism. Lancet 2009;374(9684):145-158
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.