Endocrine Abstracts (2004) 7 P1

Failure to normalise PTH during the treatment of osteomalacia

SR Peacey, D Wright & MJ Harries


Department of Diabetes and Endocrinology, Bradford Hospitals NHS Trust, Bradford, UK.


Although treatment of osteomalacia is cheap and effective, there are few data on the long-term outcomes. Studies suggest that a minority of patients fail to normalise parathyroid hormone (PTH), due to autonomous parathyroid activity and primary hyperparathyroidism is sometimes 'unmasked' during therapy. This study examined the impact of a recommended oral regimen of calcium 1000 milligrams and vitamin D3 800 international units (20 micrograms) daily, on PTH levels. 52 patients [median age 39 (16 - 77) years; 4M, 48F; 51 Asian, 1 Caucasian] with vitamin D deficiency (25-hydroxyvitamin D less than 10 micrograms per litre) and secondary hyperparathyroidism (PTH greater than 55 nanograms per litre) were identified. All patients had at least one subsequent measurement of PTH during treatment. 24 (46 percent) patients failed to normalise (group F) and 28 patients normalised (group N) PTH - post treatment PTH levels (group F vs group N) 98 (55-215) vs 41 (11-54) nanograms per litre (p less than 0.0001). Median follow up was 31 (5 - 54) months (group F) vs 13 (3 - 40) months (group N), (p=0.0006). Median age (p=0.52), basal 25-hydroxyvitamin D (p=0.91), basal PTH (p=0.13) and basal calcium (p=0.72) concentrations were similar in both groups. Post treatment calcium concentration was similar (p=0.91). Mild hypercalcaemia developed in 3.8 percent patients overall. 19 of 24 patients in group F consented to an examination of GP prescribing records. In the 12 months prior to the final elevated PTH measurement, the median number of prescriptions collected equated to only 2 (0-12) months supply. Although the number of follow up PTH measurements is few, a large proportion of patients fail to normalise PTH during standard therapy. This is likely to be related to poor adherence to long term oral medication in the majority of cases. Only a tiny number of patients develop hypercalcaemia.

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