Endocrine Abstracts

A 54-year-old lady presented with malaise, weakness, and constipation. She was found to be mildly hypercalcaemia (adjusted calcium 2.68–2.76 mmol/l; reference range 2.12–2.60 mmol/l) and was referred to local endocrinology services. Her PTH was 79 ng/l (range 10–60) and a diagnosis of primary hyperparathyroidism was made. Imaging to localise a parathyroid source was negative. She was referred to the endocrine surgeons at the Royal Victoria Infirmary, Newcastle, for consideration for parathyroidectomy and was subsequently listed routinely for neck exploration. However, her serum TSH was noted to be elevated (7.04 mU/l) and she mentioned that she could not tolerate levothyroxine tablets prescribed for primary hypothyroidism. To centralise her care, she was referred to endocrinology at the RVI regarding this. When she was seen, she complained of limb pain and had a proximal myopathy. Her vitamin D level was <10 nmol/l and the possibility of secondary hyperparathyroidism was discussed. High dose vitamin D was prescribed, in addition to levothyroxine in syrup form, and a recommendation to postpone surgery was made.

The patient felt that she was being denied a curative operation and sought a second, and then third, opinion from other endocrine surgeons. These agreed that her vitamin D deficiency should be addressed prior to contemplating surgery. When her vitamin D levels were replete, her symptoms had improved but not entirely resolved. Her adjusted serum calcium was 2.63 mmol/l, with a magnesium level at the upper end of the reference range (0.97 mmol/l; range 0.70–1.00 mmol/l) and a modestly elevated PTH (64 ng/l). A calcium:creatinine clearance ratio calculated from a 24 h urine calcium estimation was 0.007. She underwent DNA sequencing for the six exons of the calcium sensing receptor (CASR) gene and was found to be heterozygous for a pathogenic duplication in exon 4 (741 dupT), predicting a frameshift.

Common problems, in this case vitamin D deficiency, may coexist with much rarer conditions such as familial hypocalciuric hypercalcaemia. Careful investigation prevented the patient from undergoing an unnecessary surgical procedure.