Failure to normalize parathyroid hormone during treatment of vitamin D deficiency in Asian patients.

Objective: Vitamin D deficiency and osteomalacia remain commonplace within the Asian community in Bradford. The treatment of vitamin D deficiency and osteomalacia is cheap and effective, but there are few data on long-term outcomes. Studies have suggested that a minority of patients fail to normalize parathyroid hormone (PTH) levels during therapy with vitamin D. This study aimed to determine what proportion of Asian patients with vitamin D deficiency and secondary hyperparathyroidism normalize PTH levels following therapy with oral vitamin D and to examine reasons for failure to normalize PTH.

Design: This study examined the impact of an oral regimen of vitamin D 800 i.u. (20 micrograms) and calcium 1000 mg daily, on PTH levels within an endocrinology outpatient clinic. patients 51 (4M:47F) Asian patients, median age 39 years (range 16-77 years) with vitamin D deficiency (25-hydroxyvitamin D < 25 nmol/l) and secondary hyperparathyroidism (PTH > 5.7 pmol/l).

Measurements: All patients had at least one follow-up measurement of PTH and calcium during treatment. A subgroup of patients gave consent for examination of GP-prescribing records to indirectly asses adherence to therapy.

Results: PTH normalized in only 28/51 (55%) patients (group N) and failed to normalize in 23/51 (45%) patients (group F). Baseline patient characteristics including: age, basal serum 25-hydroxyvitamin D (25OHD), basal serum PTH, basal serum calcium and post treatment serum calcium, were similar in groups N and F. Mild hypercalcaemia occurred in only two (3.9%) patients. The proportion of prescriptions collected by patients in group N was 75 (17-100)% and in group F was 17 (0-100)%, P < 0.0001.

Conclusions: This study has demonstrated that long-term oral treatment with vitamin D and calcium, fails to normalize PTH in a significant proportion of patients with vitamin D deficiency and osteomalacia. This is most likely related to lack of adherence to long-term treatment. Improved ways of treating this condition need to be explored.