Your Patient’s Calcium Is Raised. Could It Be More Than a Laboratory Abnormality?
A 58-year-old patient attends for a routine health assessment. They feel reasonably well, although they mention persistent tiredness, occasional constipation and some general aches and pains. Their blood results are largely unremarkable except for one finding.
Albumin-adjusted calcium: 2.72 mmol/L.
It’s only moderately elevated and the patient has no obvious symptoms of serious illness, so does it really matter? Potentially, yes.
Because an elevated calcium concentration can sometimes be the first indication of primary hyperparathyroidism, a condition associated with osteoporosis, kidney stones and other complications. As World Osteoporosis Day approaches on 20 October, it is a useful reminder that understanding bone health involves more than simply measuring vitamin D.
The problem with apparently minor abnormalities
Routine blood profiles generate enormous amounts of information. Most results fall within reference intervals. Others sit just outside them. The challenge for clinicians is distinguishing between an isolated result that requires little action and one that deserves further investigation. Calcium is a particularly interesting example.
Many patients associate calcium almost exclusively with bones and teeth, but calcium also plays essential roles in muscle contraction, nerve signalling and other physiological processes. Its concentration in blood is tightly regulated, principally through interactions involving parathyroid hormone (PTH), vitamin D, the kidneys and bone. When calcium becomes persistently elevated, understanding why matters.
What is primary hyperparathyroidism?
The parathyroid glands are four small glands usually located behind the thyroid gland. Their principal role is regulating calcium balance. They produce parathyroid hormone, which influences calcium release from bone, renal calcium handling and intestinal calcium absorption through vitamin D activation.
In primary hyperparathyroidism, one or more glands produce excessive PTH relative to the body’s needs. The result is frequently an elevated blood calcium concentration. The NHS notes that many people with hyperparathyroidism experience few or no symptoms and discover the condition following unrelated blood testing. This makes routine pathology an important opportunity for detection.
The symptoms are surprisingly ordinary
One reason primary hyperparathyroidism can be overlooked is that symptoms are often non-specific.
Patients may describe:
- Persistent tiredness
- Muscle weakness
- Joint or bone discomfort
- Constipation
- Increased thirst
- Frequent urination
- Poor concentration
- Low mood.
These complaints occur frequently in everyday clinical practice. Most patients presenting with fatigue or constipation will not have primary hyperparathyroidism. But where these symptoms accompany persistently raised calcium, the combination becomes more meaningful.
NICE specifically recommends measuring albumin-adjusted calcium in patients with symptoms suggestive of hypercalcaemia, osteoporosis, previous fragility fractures or kidney stones.
Why adjusted calcium matters
Not all circulating calcium exists in the same form. Some is bound to proteins, particularly albumin, while some circulates as biologically active ionised calcium. Because albumin concentrations influence total calcium measurements, laboratories commonly report an albumin-adjusted calcium result.
This helps interpretation, although adjustment formulas have limitations, particularly in patients with significant disturbances of albumin or other complex clinical conditions. For investigating suspected primary hyperparathyroidism in primary care, NICE recommends albumin-adjusted calcium rather than routine ionised calcium testing. NICE defines hypercalcaemia for this pathway as albumin-adjusted calcium of 2.6 mmol/L or above. But one elevated result does not establish a diagnosis.
When should calcium be repeated?
This is where a structured testing pathway becomes valuable.
NICE recommends repeating albumin-adjusted calcium at least once when the initial concentration is:
2.6 mmol/L or above, or
2.5 mmol/L or above when features suggest primary hyperparathyroidism.
Further testing depends on the repeat result and clinical presentation. Persistent elevation provides stronger evidence that an underlying disorder of calcium regulation may be present. It also helps avoid unnecessary investigations following a single borderline result.
The next question: what is the PTH doing?
Once elevated calcium has been confirmed, parathyroid hormone becomes central to interpretation. NICE recommends measuring PTH when albumin-adjusted calcium is at least 2.6 mmol/L on two occasions, or at least 2.5 mmol/L on two occasions where primary hyperparathyroidism is suspected.
Importantly, PTH should be measured alongside a concurrent albumin-adjusted calcium result. The relationship between the two results matters more than either number alone.
Normally, elevated calcium should suppress PTH secretion. If calcium is elevated but PTH remains inappropriately normal or raised, primary hyperparathyroidism becomes an important possibility.
This illustrates a fundamental principle of endocrine pathology: A result can fall within its laboratory reference interval and still be physiologically inappropriate. A normal-range PTH therefore does not automatically exclude primary hyperparathyroidism.
Not every raised calcium result is parathyroid disease
This is an essential interpretation caveat. Hypercalcaemia has several potential causes. These include primary hyperparathyroidism, malignancy, certain medicines and excessive intake of particular supplements.
Clinical history is therefore essential. Patients should be asked about prescribed medicines, calcium-containing products, vitamin D supplements and relevant medical conditions. A suppressed PTH in someone with hypercalcaemia points towards a non-PTH-mediated cause and requires assessment for alternative diagnoses.
NICE specifically advises considering malignancy when PTH is below the laboratory reference range. The objective is not to assume that every raised calcium result indicates a benign endocrine condition, but to identify the appropriate diagnostic pathway.
What other investigations may be relevant?
Depending on the findings, useful investigations may include:
Albumin-adjusted calcium: confirms and monitors the abnormality.
Parathyroid hormone: helps determine whether the elevation is PTH-mediated.
Vitamin D: NICE recommends measuring vitamin D in people with probable primary hyperparathyroidism.
Creatinine and eGFR: assess renal function.
Phosphate: may provide additional biochemical context in selected patients.
Urinary calcium: helps distinguish primary hyperparathyroidism from familial hypocalciuric hypercalcaemia, an inherited condition that can produce persistent mild hypercalcaemia.
These investigations should follow clinical assessment and the appropriate diagnostic pathway rather than being ordered indiscriminately.
The connection with osteoporosis
Why is this particularly relevant to bone health? Excess PTH can increase bone resorption, potentially reducing bone strength over time. Untreated primary hyperparathyroidism can contribute to osteoporosis and fragility fractures. It is worth noting that it can also increase the risk of kidney stones.
For patients with confirmed primary hyperparathyroidism, NICE recommends assessment that includes renal function, renal-tract ultrasound and DXA scanning of the lumbar spine, distal radius and hip.
Blood tests cannot diagnose osteoporosis, but they can identify an underlying condition contributing to bone loss. That distinction is particularly important in preventative healthcare.
An important message for nutritionists
Nutrition professionals frequently advise patients about calcium, vitamin D, protein intake and bone health. But an elevated blood calcium result should not automatically trigger advice to reduce dietary calcium. Nor should it prompt patients to stop prescribed supplements without clinical review.
The NHS specifically advises people with hyperparathyroidism not to make dietary changes intended to lower calcium unless directed by their specialist. Where hypercalcaemia is identified, nutritionists can play an important role by reviewing supplement use and encouraging appropriate medical assessment.
Look beyond the isolated number
A raised calcium concentration may ultimately prove transient or have a relatively straightforward explanation. But persistent hypercalcaemia should not be dismissed simply because the patient feels reasonably well. For some patients, it provides an opportunity to identify primary hyperparathyroidism before complications develop.
At Viva Health Laboratories, we believe effective pathology means more than reporting whether a result falls inside or outside a reference interval. It means supporting clinicians with the investigations needed to understand what that result actually represents.
As World Osteoporosis Day approaches, there is a useful message for everyone involved in preventative healthcare:
Bone health isn’t only about what patients eat or how much vitamin D they take. Sometimes the first clue to an underlying problem is already sitting in their routine blood tests.
If you would like to speak to one of subject matter experts, please email support@vivahealthlaboratories.com