How should I approach the management of a patient with hypophosphataemia and no obvious underlying cause?

Approach to managing a patient with hypophosphataemia and no obvious underlying cause:

• First, confirm the hypophosphataemia with repeat serum phosphate measurement to exclude laboratory error.

• Conduct a thorough clinical assessment including history and examination to identify potential causes such as malnutrition, alcohol misuse, medications, or symptoms suggestive of renal phosphate wasting or endocrine disorders.

• Investigate serum calcium, parathyroid hormone (PTH), vitamin D levels, and renal function to assess for underlying metabolic or renal causes, as abnormalities in these can affect phosphate balance.

• Consider referral to a specialist (e.g., endocrinologist or nephrologist) if initial investigations do not reveal a cause or if the hypophosphataemia is severe or symptomatic.

• Management should be directed at the underlying cause if identified; if no cause is found and the patient is asymptomatic with mild hypophosphataemia, monitoring may be appropriate.

• In symptomatic or severe cases, phosphate supplementation may be considered under specialist guidance, with monitoring of serum phosphate and calcium to avoid complications.

Note: The provided NICE guidelines focus primarily on hyperphosphataemia and chronic kidney disease management and do not specifically address hypophosphataemia management; therefore, clinical judgement and specialist advice are important in these cases ¹,².