Endocrine Abstracts

Phosphate is essential for numerous physiological processes, including skeletal mineralisation, energy production, enzymatic reactions, cell membrane structure, and neurological function. Disruptions in phosphate balance, particularly hypophosphataemia, can cause significant morbidity but are often overlooked due to its exclusion from routine blood tests and the non-specific nature of its symptoms. This talk will explore the regulation of phosphate homeostasis, which is controlled by 1α,25-dihydroxyvitamin D3, parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23). These hormones govern phosphate absorption in the gut, its exchange between bone and extracellular spaces, and its excretion via the kidneys. Serum phosphate levels vary with age, making it vital to interpret results using appropriate reference ranges to avoid missed diagnoses, particularly in children. The causes of hypophosphataemia are broadly categorised into: (1) inadequate intake or absorption, often linked to malnutrition or gastrointestinal conditions; (2) redistribution, seen in conditions like diabetic ketoacidosis (DKA) treatment and refeeding syndrome; and (3) renal phosphate loss, as occurs in hyperparathyroidism or genetic conditions like X-linked hypophosphataemic rickets. Severe hypophosphataemia can lead to muscle weakness, respiratory failure, cardiac dysfunction, and bone pain due to reduced ATP production and oxygen transport. Management depends on identifying the underlying cause. Dietary supplementation is effective for nutritional deficiencies, while intravenous phosphate replacement may be necessary in acute, severe cases. Long-term treatment requires addressing the root cause, such as treating malabsorption or reducing renal phosphate losses. This presentation will outline practical approaches to diagnosing and managing hypophosphataemia, including simple diagnostic pathways and evidence-based treatments. Timely recognition and appropriate intervention are key to preventing complications, highlighting the crucial role endocrinologists play in improving outcomes for these patients.