When to evaluate

• The recommendation to not investigate routinely people with severe or symptomatic hypercalcaemia in primary care, and that these people should be admitted to hospital for urgent treatment and investigation, is based on expert opinion from a narrative review [Smellie et al, 2008]. Hence, it is only recommended to look for the underlying cause if hypercalcaemia is mild or moderate and asymptomatic.
• The recommendation to look for the underlying cause is also based on expert opinion from a narrative review that the main role of the GP in the management of hypercalcaemia is to distinguish between malignant and hyperparathyroid causes, in order to make the appropriate specialist referral [Murphy et al, 2006].
• The information that hypercalcaemia may develop in the context of known disease is also based on expert opinion from a narrative review [Smellie et al, 2008].

Reviewing medical history and looking for clinical features

• This list is based on possible causes of hypercalcaemia, and their symptoms.

Drugs or vitamin supplements

• This list is based on drugs that are known to cause hypercalcaemia.

Family history

• The recommendation to ask about any family history of primary hyperparathyroidism, familial hypocalciuric hypercalcaemia, or other endocrine tumours (that is, pituitary, adrenal, pancreatic, or thyroid tumours suggesting multiple endocrine neoplasia [MEN]) is based on a narrative review [Inzucchi, 2004]. Primary hyperparathyroidism can be familial [Chan et al, 1997], and primary hyperparathyroidism is a common feature of the rare MEN syndromes, which are partly inherited [Kumar and Clark, 2005].

Previous calcium concentrations

• The recommendation to check for any previous serum calcium concentrations in the person's notes is based on expert opinion (in a narrative review) that, in primary hyperparathyroidism, the increase in serum calcium level is usually mild and stable, or is slowly progressive over a period of years [Inzucchi, 2004].

Measuring parathyroid hormone (PTH) levels or referring to an endocrinologist

• The recommendation to measure PTH is based on consistent expert opinion in narrative reviews [Klee et al, 1988; Ralston, 1992; Carroll and Schade, 2003; Selby, 2003; Murphy et al, 2006; Smellie et al, 2008].
• The recommendation that referring the person to an endocrinologist for investigation is an alternative management option (instead of investigation) is based on feedback from CKS expert reviewers.
• The information that PTH testing is not always available in primary care is based on feedback from CKS expert reviewers. Referral to an endocrinologist is likely to be the only management option if PTH testing is not available.
• The recommendation to check with the local biochemistry laboratory whether a specific collection tube is needed, and whether the sample needs to be transported rapidly to the laboratory or taken close to the laboratory is based on expert opinion from a narrative review [Smellie et al, 2008].
• The recommendation to measure PTH before attempting to treat the hypercalcaemia is based on expert opinion (from a narrative review) that a decrease in calcium concentration can trigger PTH release, leading to the mistaken conclusion that the hypercalcaemia is PTH-dependent [Klee et al, 1988].

Additional investigations

• This list is derived from several narrative reviews [Klee et al, 1988; Davies et al, 2002; Carroll and Schade, 2003; Inzucchi, 2004; Murphy et al, 2006; Smellie et al, 2008; Waters, 2009].