Endocrine Abstracts

A 32 year old Indian woman presented with a spontaneous patella fracture. Serum alkaline phosphatase was 3694 units per litre, calcium was 3.12 millimoles per litre and phosphate 0.81 millimoles per litre. Serum PTH concentration was >150 picomoles per litre and the 25-hyroxyvitamin D3 concentration was 7 nanomoles per litre. She was found to have a 5 cm parathyroid adenoma. A 44 year old Somalian woman presented to the rheumatology clinic with a 2 year history of aching in her legs and back. Serum alkaline phosphatase was 2265 units per litre, calcium was 2.21 millimoles per litre and phosphate 0.56 millimoles per litre. 25-hydroxyvitamin D3 concentration was less than 6 nanomoles per litre and serum PTH was 125.5 picomoles per litre. On 25-hyroxyvitamin D3 replacement, her calcium rose to 2.86 millimoles per litre. Investigations revealed a 7 cm parathyroid adenoma.
Primary hyperparathyroidism in developed countries is characteristically a mild disease of women in their sixties. These cases are noteworthy for the size of their adenomas and their young age of presentation. This is similar to the presentation seen in developing countries where the prevalence of vitamin D deficiency is high. The pathogenesis of parathyroid adenoma formation in vitamin D deficient patients remains unclear. It is possible that a proportion of patients represent the coincidence of primary hyperparathyroidism and vitamin D deficiency. Alternatively, we hypothesise that autonomous four gland hyperplasia or tertiary hyperparathyroidism, might progress to adenoma formation or 'quaternary hyperparathyroidism'. Firstly, there is histological evidence that monoclonal expansions can occur on a background of generalised parathyroid hyperplasia in prolonged vitamin D deficiency. Secondly, similar sequences of events have been documented in other endocrine glands. Thirdly, we suggest that the loss of antiproliferative effect of vitamin D would lead to the expression of different proto-oncogenes than those expressed in non-familial hyperparathyroidism.