Serum 25 hydroxyvitamin D profile after single large oral doses of cholecalciferol (vitamin D3) in medical staff in North India: A pilot studyL Priyambada1, V Bhatia1, N Singh2, E Bhatia1
1 Department of Endocrinology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
2 Dietetics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0022-3859.128812 Clinical trial registration REF/2011/09/002738
Source of Support: None, Conflict of Interest: None
Clinical trial registration REF/2011/09/002738
Background: Vitamin D deficiency is widely prevalent in India and subjects who have almost no exposure to sunlight are severely deficient. Daily oral doses of cholecalciferol (vitamin D3) are costly as compared to stoss doses and further, take a long time for the serum levels to reach a plateau. Compliance to supplementation may also be better if a regimen involves single oral doses of vitamin D at specified intervals rather than daily doses. Evidence-based guidelines regarding the dosing and the frequency of dosing for prophylactic intermittent supplementation (stoss doses) in severely-deficient subjects are few. Materials and Methods: In a prospective intervention study, we serially assessed 30 asymptomatic healthy medical staff for serum 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH); (a) at baseline; (b) monthly for 3 months after single oral 60,000 units (U) cholecalciferol; (c) monthly for 3 months after 120,000 (or 180,000 for those with elevated alkaline phosphatase) U cholecalciferol; and, (d) subsequently, at 3 months after a repeat dose of 60,000 U cholecalciferol by repeated measures analysis of variance. Results: The baseline serum 25(OH)D was 7.1 ± 5.4 ng/mL (< 10 ng/mL in 85% subjects) which increased to 18.7 ± 8.9 ng/mL at 1 month after 60,000 U of cholecalciferol (P < 0.001) and decreased to 11.1 ± 5.3 ng/mL by the 3 rd month. The higher dose of 120,000 (or 180,000) U increased mean 25(OH)D to 28.9 ± 9.9 ng/mL at the end of 1 st month, declining to 17.9 ± 4.9 ng/mL (P < 0.001) at 3 months. With the subsequent 60,000 U the serum 25(OH)D was 18.4 ± 3.9 ng/mL at 3 months. PTH showed a corresponding negative trend. No hypercalcemia was observed. Conclusions: Vitamin D deficiency is highly prevalent amongst medical staff in Northern India. An initial dose of 120,000-180,000 U of cholecalciferol is required to elevate 25(OH)D out of the deficiency range. Maintenance dose is needed at 2 months.
Keywords: 25(OH)D, 25-hydroxyvitamin D, cholecalciferol, dose supplementation, Vitamin D
Vitamin D deficiency is widely prevalent in India. ,, Non-fortified food products (except fatty fish) have negligible amounts of vitamin D. Exposure to sunlight, the predominant source of vitamin D, has been much reduced by current lifestyle. Hence, pharmacological supplementation of vitamin D appears to be necessary. Daily oral doses of cholecalciferol (vitamin D3) are costly as compared to stoss doses and take a long time for the serum levels to reach a plateau. Due to its long half-life, stoss therapy [available in India as a 60,000 units (U) preparation of cholecalciferol] should be a cost-effective way to achieve and maintain normal levels of vitamin D. Compliance with supplementation may be better with single large oral doses given at regular intervals rather than daily doses. The rise of serum 25-hydroxyvitamin D [25(OH)D] is partly dependent on the level pre supplementation.  However, evidence-based guidelines regarding minimum effective (therapeutic as well as preventive) dose of vitamin D, using this preparation in populations with low serum levels of 25(OH)D, are still scant.
The current study was thus designed to assess the time course and response as measured by serum 25(OH)D levels to single intermittent doses of oral cholecalciferol.
Ethics and participants
Thirty healthy medical staff participants (18 males, 12 females) were recruited from Northern India (latitude 26°N), in early winter months of October and November. Persons with known disorders (renal, parathyroid, liver pathology) and drug intake (anticonvulsants, antituberculous agents, vitamin D supplements) that might affect vitamin D and parathyroid hormone (PTH) metabolism were excluded.
Participants were enrolled after taking IRB approval and written informed consent. The amount of sun exposure per week, clothing pattern, and use of sunscreen were recorded. Any musculoskeletal symptoms including proximal myopathy, bony pains, and fractures were carefully recorded. Dietary calcium and vitamin D intakes were estimated by a food frequency questionnaire. Baseline serum calcium, alkaline phosphatase (ALP), PTH and 25(OH)D was assessed. Cholecalciferol (Calcirol ® granules - 60,000 U /sachet, Cadila Pharmaceuticals Ltd) was administered orally under direct observation as follows, and the above parameters were assessed monthly for 3 months. This dose was chosen as this was the commonly available preparation in India.
Part 1: A single dose of 60,000 U oral cholecalciferol was administered to all 30 subjects. Their biochemical evaluation was performed monthly for 3 months.
Part 2: Subjects who consented to continue further in the study at the end of 3 months were, then, again administered another single dose of either 120,000 U (n = 8) or 180,000 U (if they had persistently elevated ALP despite having received 60,000 U in part 1 of the study, n = 5) oral cholecalciferol. Their biochemical evaluation was performed monthly for 3 months. (A total of 17 of the 30 subjects did not volunteer for study part 2 due to inability to devote time.)
Part 3: To test whether a smaller dose could now maintain the improved serum 25(OH)D levels obtained by previously taking 120,000 U or 180,000 U in part 2, a follow-up dose of 60,000 U oral cholecalciferol was again administered to 10/13 at the end of the part 2 study. Serum 25(OH)D was re-evaluated after 3 months.
Biochemical estimations were carried out immediately while sera were stored at -70°C for hormonal assay. Serum 25(OH)D was assayed by a commercial RIA kit (Diasorin, Stillwater, USA). The sensitivity of the assay was 1.5 ng/mL and the interassay coefficient of variation was 9.4% at 8.6 ng/mL and 11% at 49 ng/mL. Serum PTH was assayed using a commercial IRMA kit (Diasorin, Stillwater, USA).
Data were analyzed using SPSS version 13 (SPSS Inc., Chicago, IL, USA). The time trend of 25(OH)D levels and comparisons for difference in response between different groups were analyzed by repeated measures analysis of variance (ANOVA). All tests were two-tailed and a P value of less than 5% was considered significant.
The baseline characteristics of the study population are presented in [Table 1].
Vitamin D deficiency [serum 25(OH)D < 20 ng/mL] was seen in 90% (n = 27) of the apparently healthy medical personnel. Of these, > 90% (n = 25) had 25(OH)D < 10 ng/mL. No subject was clinically symptomatic. Sun exposure was very low (median 30 min/week). All participants were normocalcemic (mean serum calcium 9.1 ± 0.7 mg/dL). Five used sunscreen.
Following a single oral dose of 60,000 U cholecalciferol, serum 25(OH)D increased from a baseline of 7.1 ± 5.44 ng/mL to 18.7 ± 8.9 ng/mL at the end of 1 st month, followed by a decline to 11.1 ± 5.3 ng/mL at the end of 3 rd month [Figure 1]. Thus, 60,000 U cholecalciferol was unable to increase 25(OH)D levels out of the deficiency range. The differences in consecutive measurement (time trend) of 25(OH)D by repeated measures ANOVA was statistically significant (P < 0.001).
Serum PTH was 48.6 ± 24.2 pg/mL at baseline; declining to 32.8 ± 11.5 pg/mL at the end of the 1st month (P < 0.05); and rising back to 44.9 ± 17.4 pg/mL at the end of 3 months. It showed an expected inverse trend to that of serum 25(OH)D, but it was not statistically significant [negative correlation; baseline 25(OH)D and PTH (r = -0.39, P = 0.266), peak 25(OH)D and corresponding nadir PTH (r = -0.312, P = 0.38) after the first dose supplementation]. The time trend of serum PTH from baseline to 3 months was also not statistically significant, P = 0.155 [Figure 2].
Administration of 120,000 (or 180,000) U cholecalciferol was successful in raising serum 25(OH)D above 20 ng/mL. Baseline mean serum 25(OH)D in the subjects given 120,000 U was 11.28 ± 4.7 ng/mL and in those given 180,000 U was 14.6 ± 9.38 (median: 12.8) ng/mL, P = 0.406. Administration of either dose was successful in raising serum 25(OH)D above 20 ng/mL. Peak serum 25(OH)D in the subjects given 120,000 versus 180,000 U was not statistically different (30.4 ± 11.2 ng/mL vs. 23 ± 5.9 ng/mL, respectively, P = 0.24); therefore, these two subsets were merged. Serum 25(OH)D were 28.9 ± 9.9 ng/mL at the end of the 1 st month, 27.6 ± 13.9 (median: 24.1) ng/mL at the end of 2 nd month, followed by a decline to 17.9 ± 4.9 ng/mL by the end of 3 rd month. The highest 25(OH)D in any subject was 47.6 ng/mL. Time trend of 25(OH)D by repeated measures ANOVA was statistically significant (P < 0.001).
After the third month of 120,000 (or 180,000) U of supplementation, a subsequent oral dose of 60,000 U of cholecalciferol was administered. The 25(OH)D levels 3 months after the 60,000 U ''maintenance'' dose was 18.4 ± 3.9 ng/mL, which was still below the desired level. It is expected from the time trends of the previous doses that 25(OH)D levels would have been higher and likely to be more than 20 ng/mL had they been documented at time points earlier than 3 months.
Baseline ALP in the subjects was 243.4 ± 78.7 IU/L (normal ALP < 250 IU/L). Serum ALP was high [mean, 332.6 ± 59.7 (260-435) IU/L] in one third (n = 10) subjects at baseline. There was no evidence of liver disease in these subjects. Normalization of elevated ALP was seen in only one (368 IU/l to 222 IU/L at the end of 2 nd month of supplementation) of the 10 subjects following the initial 60,000 U cholecalciferol. On the basis of this observation, an arbitrary decision was taken to give these subjects a higher dose of 180,000 U instead of 120,000 U of oral cholecalciferol in part 2 of the study. ALP normalized (116, 153, and 201 IU/L) in three of the four subjects with elevated ALP who took 180,000 U after 1 month of supplementation. The baseline 25(OH)D and the initial ALP had an unexpected unexplained significant positive correlation (r = 0.374, P = 0.042).
There was no significant increase in serum calcium concentration from baseline (9.1 ± 0.7 mg/dL to 9.78 ± 0.5 mg/dL; P = 0.109) during the study, and no individual values were above the upper end of the reference range.
Comparison of difference in response of mean serum 25(OH)D over 3 months between study part 1 and 2 by repeated measures ANOVA (for the 13 subjects who took part in both study parts 1 and 2) was not significant, P = 0.172.
There were no adverse effects observed in any of the subjects.
On the basis of currently accepted minimum norms, serum 25(OH)D < 20 ng/mL was taken as vitamin D deficiency. , Analysis of various randomized controlled trials have tentatively concluded that probably 25OHD above 20 ng/mL are sufficient to normalize calcium and bone homeostasis. Though there is unclear causal relationship, s serum 25(OH)D below 20 ng/mL has an association with colon cancer, infections, cardiovascular, and metabolic diseases. 
A very high prevalence of vitamin D deficiency was observed in this study as in various other Indian studies. ,, This is likely due to clothing and indoor lifestyle which precludes exposure to the abundant sunlight. Also the brown skin pigmentation requires longer ultraviolet exposure than fairer skin, to make the same amount of vitamin D. 
Vitamin D administration in our country is often practised using regimens which can lead to toxicity (such as 600,000 U cholecalciferol as a single dose or multiple doses over a period of 24 h given for infants). These are not evidence based. The Institute of Medicine (National Institutes of Health, USA) in its 2011 recommendations advocates 600 U daily for adults, while the Endocrine Society of USA in 2011 recommended 1500-2000 U daily. , The cost of daily therapy in doses of 1000 U per day, in India, at the time of writing, is10-12 times greater than an equivalent dose given once in 2 months.
The change in concentration of 25(OH)D in response to a single large (100,000 U) oral dose of cholecalciferol has been documented by Ilahi et al.,  where they found that serum 25(OH)D reaches a peak level by day 7, and then has a linear decline. The mean value fell below 32 ng/mL by 70 days. Hence, vitamin D administered as intermittent therapy is scientific, improves patient compliance, and also makes directly observed therapy feasible.
Similar data were published by Romagnoli et al., and Cipriani et al. , These authors showed that peak 25(OH)D after a single oral dose of 300,000 U or 600,000 U respectively occurs at 1 week, plateaus till 3 weeks, and falls to baseline by 2 or 2 and a half months. Their subjects, however, had higher baseline 25(OH)D, and this important determinant of response to therapy was strikingly low in our subjects.  A gradual decline in serum 25(OH)D levels was seen after the 1 st month of supplementation, reaching baseline values by the end of 3 rd month. Hence, larger doses will merely raise the peak, but not delay the decline of serum 25(OH)D significantly.
Our pilot study suggests that for North Indian adults with a severe vitamin D deficiency [25(OH)D < 10 ng/mL], one dose of oral 60,000 U is not sufficient to raise 25(OH)D (18.7 ± 8.9 ng/mL) into the normal range at 1 month post administration. The serum 25(OH)D declines further with time. However, a single oral dose of 120,000 or 180,000 U of cholecalciferol was sufficient to raise serum 25(OH)D into the normal range, while at the same time not giving rise to hypervitaminosis D or hypercalcemia. The improved serum 25(OH)D lasted only for 2 months. At the 3 rd month after 120,000/180,000 U cholecalciferol, the mean 25(OH)D declined back into the deficient range (17.9 ± 4.9 ng/mL). A subsequent maintenance dose of 60,000 U was only able to maintain 25(OH)D at a similar level (18.4 ± 3.9 ng/mL) after 3 months but was not able to improve it to the optimum level. A maintenance dose at a shorter interval than 3 months would probably be effective in maintaining desired levels. A higher maintenance dose may be an alternative but as we have seen from previous studies, increasing the dose would probably increase the peak of response without significantly increasing the duration of the response. ,
Therefore, at least 2 monthly dosing appears necessary. We believe that stoss therapy will result in better compliance as compared to daily doses especially in people with busy lifestyle.
In another study of Indian subjects with low baseline levels of 25(OH)D, an exuberant response, 4.8 ± 3.5 ng/mL increased to 31.6 ± 15.5 ng/mL, was observed at the end of three doses of monthly 60,000 U cholecalciferol (total dose of 180,000 U over 3 months in the summer season). The baseline serum 25(OH)D, vitamin D dose and the response were comparable to the present study.  The authors concluded the impressive increment in the study group was likely due to the summer season. The study design did not allow the reader to conclude on the adequacy of less frequent dosing than once a month.
In a retrospective cohort study by Demetriou et al.,  50000 U D2 supplementation (weekly or 2-weekly loading and maintenance 2-weekly doses) in subjects with low baseline 25(OH)D2 (4.2 ± 4.3 ng/mL) increased 25(OH)D2 to 34.6 ± 12.3 ng/mL. There was no toxicity. Of course, our study differed from theirs in important aspects as we supplemented D3 and not D2, as a single-dose supplementation and the total supplementation dose was less.
Toxicity caused by excessive doses of vitamin D is not uncommon; especially in infants, in the elderly or those affected by diseases such as renal failure. , Furthermore, recent information on intermittent therapy with higher doses of the order of 500,000 U once a year in elderly subjects from New Zealand showed increased risk for falls and fractures.  The greatest incidence of falls occurred in the initial 3 months after the dose. The authors speculated that high serum levels of vitamin D or metabolites resulting from the large annual dose, subsequent decrease in the levels, or both might be causal; and large annual dose stoss therapy need further evaluation.
Thus, in the interests of economy as well as minimizing toxicity, it appears that an initial dose of 120,000 (or at most 180,000) U of cholecalciferol is necessary and sufficient for initiating a preventive regimen for young and middle-aged healthy men and women who are at risk for vitamin D deficiency due to poor sun exposure. Additional doses will be needed at least 2 monthly.
Our study has some limitations. It is a pilot study, with small number of subjects from a very homogenous background. There were dropouts in the second and third parts. In part 2 of the study, subjects received 2 different types of doses. Thus, these results cannot be extrapolated to other groups of subjects and need to be replicated in larger studies with good follow-up. We could not study serum calcium earlier than 1 month of the dose and could not study urine calcium/creatinine ratio. Our study does not have a comparator arm and we were unable to study different doses simultaneously. Nevertheless, we believe our results do give valuable preliminary insight, helping clinicians to move towards more physiologic, less expensive and feasible replacement regimens, for those people whose lifestyle limitations preclude them from having more sun exposure. Such a regimen can also be easily incorporated into a program, where administration of vitamin D under direct observation would be desirable.
We acknowledge the medical personnel whose cooperation made the study possible. We acknowledge Mr PK Awasthi for technical assistance in the 25OHD assay, and Mr Arjun Singh for other logistical help.
[Figure 1], [Figure 2]