Which of the following is best method for monitoring the treatment and resolution of vitamin D deficiency?

Ans. a. (Serum calcium levels) (Ref. Harrison's Principles of Internal Medicine 16th Edition 2249).# The most specific screening test for vitamin D deficiency in otherwise healthy individuals is a serum 25(OH)D level.# Radiologic features of vitamin D deficiency in children include a widened, expanded growth plate, characteristic ofrickets.# A specific radiologic feature of osteomalacia, whether associated with phosphate wasting or vitamin D deficiency, ismilkman's fractures, pseudofractures, or Looser's zones.TREATMENT & MONITORING OF VITAMIN D DEFICIENCY# Daily intake of a multivitamin preparation that contains 400 IU of vitamin D is often insufficient to prevent vitamin D deficiency.# Based on the observation that 800 IU of vitamin D, with calcium supplementation, decreases the risk of hip fractures in elderly women, 800 IU is considered to be a more appropriate daily dosage for prevention of vitamin D deficiency.# The safety margin for vitamin D is large, and vitamin D toxicity is usually observed only in patients taking doses >40,000 IU daily.# The most efficacious methods to monitor treatment and resolution of vitamin D deficiency are serum and urinary calcium measurements.- For patients who are vitamin D replete and are taking adequate calcium supplementation, the 24-h urinary calcium excretion should be in the range of 100 to 250 mg/24 h.- Lower levels suggest problems with adhering to the treatment regimen or with absorption of calcium or vitamin D supplements.# The 25(OH)D level can be re-measured to address the latter, although the half-life of this metabolite is long (3weeks) and levels may continue to increase for many months on a stable regimen.# Urinary calcium excretion >250 mg/24 h predisposes to nephrolithiasis and should prompt a reduction in vitamin D dosage and/or calcium supplementation.