**3. Results**

The average values for calcidiol and PTH plasma levels from the totality of the collections were 27.4 ± 7.7 ng/mL and 33.2 ± 17.3 pg/mL, respectively. Calcidiol levels overtook 30 ng/mL (Vitamin D sufficiency) in 236 individuals (39.6%), oscillated between 20 and 29 ng/mL (Vitamin D insufficiency) in 266 (44.6%), and were lower than 20 ng/mL (Vitamin D deficiency) in 94 (15.8%). The average values for calcium and phosphorus were 9.9 ± 0.5 and 4.6 ± 0.5 mg/dL, respectively. No values for hypo-/hypercalcemia or hypo-/hyperphosphatemia were detected. The frequency of hyperparathyroidism was significantly higher in the deficient vitamin D (11.6%) and insufficient vitamin D (6.6%) groups, whereas the prevalence of hyperparathyroidism was lowest in the sufficient vitamin D (2.3%) group (p = 0.005).

**Table 1** shows the distribution of the presumed risk factors for hypovitaminosis D (sex, age group, place of residence, season of blood sample collection, and nutrition status).

**Table 2** shows and compares the mean values for the clinical characteristics and biochemical determinations according to the risk factors for hypovitaminosis D. Mean PTH values were significantly higher (p < 0.05) in females. The average phosphorous values were significantly higher in males (p < 0.05). No significant differences were


#### **Table 1.**

*Demographics and clinical characteristics of the participants in the study.*

detected in age, nutrition situation, calcium, and calcidiol after the comparison between sexes. Calcidiol and phosphorus levels were significantly higher (p < 0.05) in the school group, whereas the average values for PTH were significantly higher in adolescents (p < 0.05). There were not any significant differences in Calcium levels between the age groups. Those individuals whose residence was in rural areas showed mean values for calcium and calcidiol significantly higher, whereas those individuals living in urban areas had PTH mean values significantly higher. There were no significant differences regarding age, BMI (Z-score), and phosphorous among individuals living in both areas. The lowest calcidiol levels corresponded to spring (26.1 ± 6.2 ng/ mL), and they reached a maximum in the summer (34.5 ± 8.0 ng/mL); meanwhile, the lowest parathyroid hormone levels corresponded to summer (26.6 ± 10.1 pg./mL) and reached a maximum value in autumn (37.8 ± 17.2 pg./mL). There were not any significant differences in calcium and phosphorus levels in each season. Mean values of calcidiol and PTH were significantly lower and higher (p < 0.05), respectively, in the group of severe obesity than in other groups with different nutritional situations (normal, overweight, and obesity). There were no significant differences in calcidiol and phosphorous mean values among the different groups.

**Table 3** exposes and compares the prevalence of the different calcidiol levels in relation to analyzed associated factors in hypovitaminosis D. We did not detect significant differences in the prevalence of the different levels in calcidiol status in relation to sex. However, the prevalence of vitamin D deficiency was significantly higher in the group of adolescents with respect to school children and rural environment. In the same way, individuals with severe obesity showed a prevalence of vitamin D deficiency significantly higher than those in different nutritional situations.

**19**

**Item** Sex Females

Males Significance (p)

Age group School Adolescent Significance (p)

Residence Urban

Rural Significance (p)

Season

Winter Spring Summer Autumn Significance (p)

Nutritional status

Normal Overweight

Obesity Severe obesity Significance (p)

**Table 2.**

9.62 ± 3.34 10.43 ± 2.6 11.09 ± 2.4 11.1 ± 3.28

<0.001

−0.64 ± 0.94

1.37 ± 0.29 2.46 ± 0.28 4.66 ± 2.24

<0.001 *Clinical and biochemical characteristics according to the presumed risk factors for hypovitaminosis D (M ± DE).*

9.98 ± 0.36 10.02 ± 0.38 10.05 ± 0.36

9.96 ± 0.36

0.447

4.59 ± 0.57 4.62 ± 0.55 4.66 ± 0.62 4.54 ± 0.72

0.721

28.18 ± 7.7 27.65 ± 7.35 26.19 ± 7.01 23.09 ± 8.24

<0.001

31.11 ± 15.58

33.12 ± 16.25

39.9 ± 20.26

45.22 ± 22

<0.001

9.78 ± 3.07 10.24 ± 3.14 10.44 ± 3.28

9.65 ± 3.56

0.182

0.49 ± 2.5 0.55 ± 1.74 0.46 ± 2.73 0.33 ± 1.85

0.806

10.04 ± 0.33 10.02 ± 0.37

9.97 ± 0.29 9.93 ± 0.40

0.119

4.57 ± 0.56 4.61 ± 0.56 4.66 ± 0.64 4.60 ± 0.59

0.731

26.54 ± 7.39 26.11 ± 6.25 34.52 ± 8.05 26.26 ± 7.42

<0.001

31.02 ± 18.03

32.28 ± 18.05

26.65 ± 10.06

37.88 ± 17.21

<0.001

**Age (years)**

9.88 ± 3.18 9.98 ± 3.44

0.720 7.19 ± 2.08 12.62 ± 1.62

<0.001 10.06 ± 3.28

9.67 ± 3.31

0.171

0.44 ± 2.11 0.47 ± 1.85

0.885

9.97 ± 0.35 10.05 ± 0.37

0.008

4.60 ± 0.58 4.61 ± 0.60

0.807

26.46 ± 7.74 29.02 ± 7.47

<0.001

34.49 ± 17.64 30.89 ± 16.76

0.019

0.17 ± 1.78

0.71 ± 2.2

<0.001

10.01 ± 0.38

9.97 ± 0.34

0.157

4.73 ± 0.54 4.47 ± 0.61

<0.001

28.50 ± 7.44 26.22 ± 7.86

<0.001

0.47 ± 1.69 0.41 ± 2.10

0.720

10.01 ± 0.37

9.98 ± 0.36

0.348

4.52 ± 0.59 4.71 ± 0.57

<0.001

26.88 ± 7.75 27.98 ± 7.69

0.083

35.72 ± 18.46 29.90 ± 15.27

<0.001

**BMI (Z-score)**

**Calcium (mg/dl)**

**Phosphorus (mg/dl)**

**Calcidiol (ng/ml)**

**PTH (pg/ml)**

*Vitamin D Deficiency in Children*

*DOI: http://dx.doi.org/10.5772/intechopen.89208*

30.87 ± 15.42 35.58 ± 18.91

<0.001


#### *Vitamin D Deficiency in Children DOI: http://dx.doi.org/10.5772/intechopen.89208*

*Vitamin D Deficiency*

Sex

Age group

Residence

Season of study

Nutritional status

**Table 1.**

detected in age, nutrition situation, calcium, and calcidiol after the comparison between sexes. Calcidiol and phosphorus levels were significantly higher (p < 0.05) in the school group, whereas the average values for PTH were significantly higher in adolescents (p < 0.05). There were not any significant differences in Calcium levels between the age groups. Those individuals whose residence was in rural areas showed mean values for calcium and calcidiol significantly higher, whereas those individuals living in urban areas had PTH mean values significantly higher. There were no signifi

**Item N (%)**

Female 340 (43.5%) Male 262 (56.5%)

Child 299 (49.7%) Adolescent 303 (50.3%)

Urban 394 (65.6%) Rural 207 (34.4%)

Winter 180 (29.9%) Spring 131 (21.8%) Summer 106 (17.6%) Autumn 185 (30.7%)

Normal weight 393 (67.3%) Overweight 69 (11.8%) Obesity 68 (11.6%) Severe obesity 54 (9.2%)

cant differences regarding age, BMI (Z-score), and phosphorous among individuals living in both areas. The lowest calcidiol levels corresponded to spring (26.1 ± 6.2 ng/ mL), and they reached a maximum in the summer (34.5 ± 8.0 ng/mL); meanwhile, the lowest parathyroid hormone levels corresponded to summer (26.6 ± 10.1 pg./mL) and reached a maximum value in autumn (37.8 ± 17.2 pg./mL). There were not any significant differences in calcium and phosphorus levels in each season. Mean values of calcidiol and PTH were significantly lower and higher (p < 0.05), respectively, in the group of severe obesity than in other groups with different nutritional situations (normal, overweight, and obesity). There were no significant differences in calcidiol

**3** exposes and compares the prevalence of the different calcidiol levels

in relation to analyzed associated factors in hypovitaminosis D. We did not detect significant differences in the prevalence of the different levels in calcidiol status in relation to sex. However, the prevalence of vitamin D deficiency was significantly higher in the group of adolescents with respect to school children and rural environ

ment. In the same way, individuals with severe obesity showed a prevalence of vita

min D deficiency significantly higher than those in different nutritional situations.

and phosphorous mean values among the different groups.

*Demographics and clinical characteristics of the participants in the study.*

**18**

**Table**

**Table 2.** *Clinical and biochemical characteristics according to the presumed risk factors for hypovitaminosis D (M ± DE).*





#### **Table 3.**

*Prevalence of the different calcidiol levels in relation to the presumed risk factors for hypovitaminosis D.*

#### **Figure 1.**

*Prevalence of vitamin D status according to seasons.*

**Figure 1** presents the prevalence of hypovitaminosis D (deficiency and insufficiency) according to the seasons of the year in healthy pediatric population. The levels of vitamin D during summer was sufficient in 80% of the individuals; this level substantially decreased in autumn and winter (hypovitaminosis was detected in 65.6% and 62.7% during autumn and winter, respectively) and got to the lowest point in spring, a period that revealed a prevalence of hypovitaminosis of 72.7%.

**21**

*Vitamin D Deficiency in Children*

**Figure 2.**

**Figure 3.**

*DOI: http://dx.doi.org/10.5772/intechopen.89208*

*Calcidiol levels (ng/ml ± CI 95%) throughout the year (ANOVA, p < 0.001).*

during the winter and spring months.

26.1 pg/mL, CI 95%: 23.0–29.2).

**Figure 2** states the average values for calcidiol levels along the months of the year (ANOVA, p < 0.001), showing the highest levels during the summer months (July: 32.6 ng/mL, CI 95%: 29.7–35.5; August: 33.6 ng/mL, CI 95%: 31.2–36; and September: 33.5 ng/mL, CI 95%: 31.4–35.6); in contrast, these levels were lower

**Figure 3** presents the PTH levels (average) in the different months of the year (ANOVA, p < 0.001). The autumn months show the highest PTH levels (October: 39.8 pg/mL, CI 95%: 35.4–43.6; November: 37.1 pg/mL, CI 95%: 34.1–34.1; and December: 36.0, CI 95%: 31.7–40.3) and the end of spring (May: 32.8 pg/mL, CI 95%: 29.0–36.6 and June: 33.0 pg/mL, CI 95%: 29.0–37.0); in contrast, these levels were lower in the summer months (July: 25.1 pg/mL, CI 95%: 21.9–28.3 and August:

A significant correlation (p < 0.001) between calcidiol and parathyroid hormone levels (r = −0.24) was observed; calcium and PTH plasma levels (r = −0.20) are also correlated. A significant correlation was detected between age and calcidiol

**Table 4** illustrates the multiple logistic regression analysis for the presumed predictors of vitamin D status. The female sex, adolescence, season of blood sample collection (autumn, winter, and spring), an urban residence, and severe obesity showed an association with an increased risk of vitamin D insufficiency. Adolescence, season of blood sample collection (autumn and winter), urban residence, and severe obesity

levels (r = −0.15) and also between age and PTH levels (r = 0.18).

*PTH levels (pg/ml ± CI 95%) in the different months of the year (ANOVA, p < 0.001).*

revealed an association with an increased risk of vitamin D deficiency.

#### **Figure 2.**

*Vitamin D Deficiency*

Sex

Age group

Residence

Season

**Table 3.**

Nutritional status

**Item Deficiency**

**N (%)**

Males 38 (14.6%) 105 (40.4%) 117 (45%)

Adolescent 61 (20.3%) 135 (45%) 104 (34.7%)

Rural 19 (9.2%) 91 (44.2%) 96 (46.6%)

Winter 40 (21.1%) 79 (41.6%) 71 (37.4%)

Summer 4 (5.3%) 11 (14.7%) 60 (80%) Autumn 33 (16.3%) 100 (49.3%) 70 (34.5%)

Normal 46 (11.8%) 176 (45.1%) 168 (43.1%)

Obesity 12 (18.2%) 33 (50%) 21 (31.8%) Severe obesity 20 (37.7%) 23 (43.4%) 10 (18.9%)

**Insufficiency N (%)**

Females 56 (16.7%) 161 (47.9%) 119 (35.4%) 5.65 (0.059)

School 31 (11.1%) 131 (44.3%) 132 (44.6%) 11.696 (0.003)

Urban 75 (19.3%) 175 (45%) 139 (35.7%) 12.671 (0.002)

Spring 17 (13.3%) 76 (59.4%) 35 (27.3%) 69.12 (<0.001)

Overweight 11 (15.9%) 27 (39.1%) 31 (44.9%) 30.135 (<0.001)

*Prevalence of the different calcidiol levels in relation to the presumed risk factors for hypovitaminosis D.*

**Sufficiency N (%)**

**Chi2 (p)**

**20**

**Figure 1.**

*Prevalence of vitamin D status according to seasons.*

**Figure 1** presents the prevalence of hypovitaminosis D (deficiency and insufficiency) according to the seasons of the year in healthy pediatric population. The levels of vitamin D during summer was sufficient in 80% of the individuals; this level substantially decreased in autumn and winter (hypovitaminosis was detected in 65.6% and 62.7% during autumn and winter, respectively) and got to the lowest point in spring, a period that revealed a prevalence of hypovitaminosis of 72.7%.

*Calcidiol levels (ng/ml ± CI 95%) throughout the year (ANOVA, p < 0.001).*

#### **Figure 3.** *PTH levels (pg/ml ± CI 95%) in the different months of the year (ANOVA, p < 0.001).*

**Figure 2** states the average values for calcidiol levels along the months of the year (ANOVA, p < 0.001), showing the highest levels during the summer months (July: 32.6 ng/mL, CI 95%: 29.7–35.5; August: 33.6 ng/mL, CI 95%: 31.2–36; and September: 33.5 ng/mL, CI 95%: 31.4–35.6); in contrast, these levels were lower during the winter and spring months.

**Figure 3** presents the PTH levels (average) in the different months of the year (ANOVA, p < 0.001). The autumn months show the highest PTH levels (October: 39.8 pg/mL, CI 95%: 35.4–43.6; November: 37.1 pg/mL, CI 95%: 34.1–34.1; and December: 36.0, CI 95%: 31.7–40.3) and the end of spring (May: 32.8 pg/mL, CI 95%: 29.0–36.6 and June: 33.0 pg/mL, CI 95%: 29.0–37.0); in contrast, these levels were lower in the summer months (July: 25.1 pg/mL, CI 95%: 21.9–28.3 and August: 26.1 pg/mL, CI 95%: 23.0–29.2).

A significant correlation (p < 0.001) between calcidiol and parathyroid hormone levels (r = −0.24) was observed; calcium and PTH plasma levels (r = −0.20) are also correlated. A significant correlation was detected between age and calcidiol levels (r = −0.15) and also between age and PTH levels (r = 0.18).

**Table 4** illustrates the multiple logistic regression analysis for the presumed predictors of vitamin D status. The female sex, adolescence, season of blood sample collection (autumn, winter, and spring), an urban residence, and severe obesity showed an association with an increased risk of vitamin D insufficiency. Adolescence, season of blood sample collection (autumn and winter), urban residence, and severe obesity revealed an association with an increased risk of vitamin D deficiency.


#### **Table 4.**

*Multiple logistic regression analysis for the presumed risk factor for hypovitaminosis (deficiency and insufficiency).*
