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300000 IU of vitamin D every 3 months may not have been enough – July 2010

Heterogeneity in Serum 25-Hydroxy-Vitamin D Response to Cholecalciferol in Elderly Women with Secondary Hyperparathyroidism and Vitamin D Deficiency.

J Am Geriatr Soc. 2010 Jul 14.
Giusti A, Barone A, Pioli G, Girasole G, Razzano M, Pizzonia M, Pedrazzoni M, Palummeri E, Bianchi G.
Department of Gerontology and Musculoskeletal Sciences, Galliera Hospital, Genoa, Italy.

OBJECTIVES: To compare the effects on parathyroid hormone (PTH) and 25-hydroxy-vitamin D (25(OH)D) of two dosing regimens of cholecalciferol in women with secondary hyperparathyroidism (sHPTH) and hypovitaminosis D and to investigate variables affecting 25(OH)D response to cholecalciferol.

DESIGN: Randomized-controlled trial with 6-month follow-up.

SETTING: Two osteoporosis centers in northern Italy.

PARTICIPANTS: Sixty community-dwelling women aged 65 and older with sHPTH and hypovitaminosis D, creatinine clearance greater than 65 mL/min and without diseases or drugs known to influence bone and vitamin D metabolism.

INTERVENTION: Cholecalciferol 300,000 IU every 3 months, once at baseline and once at 3 months (intermittent D(3) group) or cholecalciferol 1,000 IU/day (daily D(3) group). MEASUREMENTS: Serum PTH, 25(OH)D, calcium, bone-specific alkaline phosphatase, beta-C-terminal telopeptide of type I collagen, phosphate, 24-hour urinary calcium excretion.

RESULTS: The two groups had similar baseline characteristics. All participants had vitamin D deficiency 25(OH)D<20 ng/mL), and 36 subjects (60%) had severe deficiency (<10 ng/mL), with no difference between the groups (severe deficiency: intermittent D(3) group, n=18; daily D(3) group, n=18). After 3 and 6 months, both groups had a significant increase in 25(OH)D and a reduction in PTH.

Mean absolute increase+/-standard deviation of 25(OH)D at 6 months was higher in the intermittent D(3) group (22.7+/-11.8 ng/mL) than in the daily D(3) group (13.7+/-6.7 ng/mL, P<.001), with a higher proportion of participants in the intermittent D(3) group reaching desirable serum concentration of 25(OH)D >/= 30 ng/mL (55% in the intermittent D(3) group vs 20% in the daily D(3) group, P<.001).

Mean percentage decrease of PTH in the two groups was comparable, and at 6 months, a similar proportion of participants reached normal PTH values. 25(OH)D response to cholecalciferol showed a wide variability.

In a logistic regression analysis, body mass index and type of treatment appeared to be significantly associated with normalization of 25(OH)D values.

CONCLUSION: Cholecalciferol 300,000 IU every 3 months was more effective than 1,000 IU daily in correcting vitamin D deficiency, although the two groups achieved similar effects on PTH at 6 months. Only 55% of the higher-dose intermittent group reached desirable concentrations of 25(OH)D, suggesting that yet-higher doses will be required for adequate vitamin D repletion. PMID: 20646099

Note: 300,000 IU over 3 months = 3300 IU per day - nope, not enough