Acromegaly with hypophosphataemia: McCune-Albright syndrome

A 38-year-old man presented with excessive height gain and progressive enlargement of the extremities since childhood. This was compounded by lower limb deformities over the past 5 years. On examination, his height was 196 cm, he had macroglossia, acral enlargement, seborrhoea, hyperhidrosis-suggesting acrogigantism. He had facial asymmetry, wind-swept deformity of lower limbs and a café-au-lait macule over his trunk. Investigations revealed normal-sized pituitary gland with dysplastic cranial bones. Isotope bone scintigraphy was suggestive of polyostotic fibrous dysplasia. A diagnosis of McCune-Albright syndrome was made and trans-sphenoidal hypophysectomy was undertaken. He had persistent hypophosphataemia. Tubular reabsorption of phosphate adjusted for glomerular filtration rate was low and serum FGF-23 level was high. Ga-DOTATATE scintigraphy showed somatostatin-receptor expression in all the dysplastic lesions. FGF-23 produced by the bony lesions could counteract the phosphate-retaining effect of GH excess resulting in hypophosphataemia, which further worsened following hypophysectomy.