Response of a single 'mega intramuscular dose' of vitamin D on serum 25OHD and parathyroid hormone levels.

OBJECTIVE To determine the changes produced in serum 25OHD and iPTH levels after 600,000 IU of injection cholecalciferol in volunteers. STUDY DESIGN Interventional study. PLACE AND DURATION OF STUDY Section of Chemical Pathology, Department of Pathology and Microbiology, the Aga Khan University Hospital, Karachi, from June 2009 - June 2010. METHODOLOGY Volunteers of either gender aged 18-40 years with known 25OHD, calcium (Ca), creatinine (Cr) and phosphorous (P) levels were included in the study. Subjects on therapy like vitamin D and calcium supplements, corticosteroids or anti-epileptic medicines, primary hyperparathyroidism and hypercalcaemia, with co-morbidity like renal failure, liver disease and history of malabsorption, diarrhea or hyperthyroidism were excluded. All volunteers were given an intramuscular injection of vitamin D3 (cholecalciferol, 600,000 IU). After 8 weeks, serum 25OHD, iPTH, Ca and P levels were determined again. For 25OHD level, cut-off of ² 50 nmol/l was defined as deficient, 50-75 nmol/l as insufficient and ³ 75 as optimal level. RESULTS Mean 25OHD and iPTH levels were 35.06 ± 16.6 nmol/l and 81.15 ± 76.78 pg/ml respectively at baseline. Seventeen volunteers were 25OHD deficient. Five had high iPTH levels (25%) (mean 156 ± 123.7 pg/ml). 25OHD and iPTH showed a significant inverse correlation at baseline (< 0.01). After 8 weeks of injection vitamin D 25OHD levels became optimal in 6 subjects (35%) [mean 92.9 ± 16.6 nmol/l]. It remained low in 5 volunteers (25%) [mean 41.6 ± 9.6 nmol/l] while insufficient levels were seen in 9 volunteers (40%) [mean 63.3±5.8 nmol/l]. Follow-up mean Ca, P and iPTH were 2.25 mmol/l (± 0.09), 1.1 (± 0.1) and 47.52 pg/ml (± 22.56) respectively. A significant increase in mean 25OHD level was seen at follow-up (p < 0.01), while the change in PTH was insignificant (p=0.05). CONCLUSION Single mega-dose of cholecalciferol achieved optimal levels of 25OHD in 35% of subjects after eight weeks of supplementation.