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Dear Editor,

We read with interest the recent excellent review Clinical and genetic aspects of calcium-sensing disorder by Simon Pearce¹. We Would like to comment on one point regarding Familial Benign Hypocalciuric Hypercalcaemia (FBHH).

Dr. Pearce quite rightly refers to two key papers^2,3 which are often quoted to support. the widely held belief that although up to a fifth of patients with FBHH have mildly, elevated parathyroid hormone (PTH), generally, PTH is within the normal range in FBHH. However this does not reflect our experience. In studies on six well characterised kindreds with FBHH, we have measured PTH on a total of 20 patients with the condition. Of these patients, 5 have a PTH within the reference range, i.e 75% have a PTH outwith the reference range⁴. We would be interested to hear your readers’ views on this.

Does our experience simply reflect the nature of the cau-sative mutations in our local population or (as one would expect from mutations which lead to an elevated “set point of the receptor controlling PTH secretion) do PTH levels in FBHH tend to be higher than the current literature suggests?

Yours sincerely

References:

1. Pearce SHS. Clinical and genetic aspects of calcium-sensing disorders. CME Bulletin Endocrinology and Diabetes 1999; 2: 44-46.

2. Law WM,Heath H. Familial benignhypercalcaemia (hy-pocalciuric hypercalcaemia). Clinical and pathogenetic study of 21 families. Ann Int Med 1985; 102:511-519.

3. Heath H. Familial benign (hypocalciuric) hypercalcaemia, a troublesome mimic of mild primary hyperparathyroidism. Endocrinol Metab Clin N America 1989.18:723-740.

4. Bell E. Dryrburgh F. Muintaz M, Dargic R, MacIntosh G, Hinnie J. A possible biochemical test for distinguishing primary hyperparathyroidism from familial hy-pocalciuric hypercalcaemia. Proceedings of the Association of Clinical Biochemists National Meeting 1998:69.