Endocrine Abstracts

29-year old woman was admitted with tetany & severe hypocalcaemia despite treatment with high dose alpha-calcidiol (6 micrograms/day) and Calcium (8.0 g/day).

PMH: Six years previously she had subtotal thyroidectomy for non-toxic goitre in another Department. Postoperatively she required Thyroxine, but was lost to formal endocrine follow-up. Five years later she presented with abdominal discomfort and occasional diarrhoea. Investigations performed by gastroenterologists demonstrated microcytic anaemia (HB 9.8 g/dl, MCV 63 fl). Gastroscopy revealed gastritis and positive test for H. pylori. Eradication therapy was prescribed and she was discharged on iron supplements. Subsequently she was referred to Endocrine Clinic because of continuing ill-health. Examination revealed positive Chvostek`s and Trousseau signs. Plasma calcium of 1,8 mmol/l (ref range: 2.2 to 2.55) was thought to be related to hypoparathyroidism caused by thyroidectomy. Hypocalcaemia however, failed to normalise, and in fact worsened, despite gradual increase in the dose of alpha-calcidiol. She denied any compliance problems with her medication.

Investigations on admission: Albumin Adjusted Ca 1.18 mmol/l, Phosphate 1.21 mmol/l (0.87 to 1.45), Mg 0.76 mmol/l (0.6 to 1.45), Urea 11 mg/dl (20 to 40), Creatinine 0.6 mg/dl (0.6 to 1.4), TSH 9.21 mIU/l, total cholesterol 98 mg/dl (140-200), FBC: Hb 10.7 g/dl, MCV 78.3 fl, transferrin saturation 16% (25 to 35%), urinary Calcium 0.26 mmol/24 hr (2.5 to 6.25). Transient increase in Calcium concentrations was noted only after intravenous Calcium administration.

Given the combination of low Calcium, normal phosphate, iron-deficiency anaemia and poor response to oral medication the possibility of a malabsorption was raised. Repeated gastroscopy demonstrated villous atrophy consistent with coeliac disease. PTH level of 63.6 pg/ml (15 to 65) confirmed the presence of functional parathyroids. Gluten-free diet was started. Her Calcium levels are now normal on lower dose of alpha-calcidiol.

Conclusions: Hypocalcaemia after thyroidectomy cannot be automatically assumed to be caused by post-operative hypoparathyroidism and/or compliance problems. Other possible causes of hypocalcaemia should be considered and appropriately investigated.