Fischer, Philip R.

A retrospective review identified 99 adolescents (79% female) referred to a tertiary care center to evaluate the relationship between symptoms of orthostatic intolerance and chronic pain. Regression analysis indicated that functional disability was strongly associated with pain intensity (P < .001) and depression (P = .024). The association between functional disability and number of symptoms of orthostatic intolerance trended toward significance (P = .057). Meeting a threshold heart rate increment of 30 beats per minute on head-up tilt was not associated with functional disability (P = .188). Separate regression analysis of female patients showed similar results to the full sample but with a stronger relationship between depression and functional disability and a weaker relationship between heart increment and functional disability. In this sample of adolescents with symptoms of orthostatic intolerance and chronic pain, pain intensity and depression were associated with functional status, but postural tachycardia was not. Further research is needed to clarify potential gender differences.

Abstract Children with calcium-deficiency rickets may have increased vitamin D requirements and respond differently to vitamin D2 and vitamin D3. Our objective was to compare the metabolism of vitamins D2 and D3 in rachitic and control children. We administered an oral single dose of vitamin D2 or D3 of 1.25 mg to 49 Nigerian children—28 with active rickets and 21 healthy controls. The primary outcome measure was the incremental change in vitamin D metabolites. Baseline serum 25-hydroxyvitamin D [25(OH)D] concentrations ranged from 7 to 24 and 15 to 34 ng/mL in rachitic and control children, respectively (p &lt; .001), whereas baseline 1,25-dihydroxyvitamin D [1,25(OH)2D] values (mean ± SD) were 224 ± 72 and 121 ± 34 pg/mL, respectively (p &lt; .001), and baseline 24,25-dihydroxyvitamin D [24,25(OH)2D] values were 1.13 ± 0.59 and 4.03 ± 1.33 ng/mL, respectively (p &lt; .001). The peak increment in 25(OH)D was on day 3 and was similar with vitamins D2 and D3 in children with rickets (29 ± 17 and 25 ± 11 ng/mL, respectively) and in control children (33 ± 13 and 31 ± 16 ng/mL, respectively). 1,25(OH)2D rose significantly (p &lt; .001) and similarly (p = .18) on day 3 by 166 ± 80 and 209 ± 83 pg/mL after vitamin D2 and D3 administration, respectively, in children with rickets. By contrast, control children had no significant increase in 1,25(OH)2D (19 ± 28 and 16 ± 38 pg/mL after vitamin D2 and D3 administration, respectively). We conclude that in the short term, vitamins D2 and D3 similarly increase serum 25(OH)D concentrations in rachitic and healthy children. A marked increase in 1,25(OH)2D in response to vitamin D distinguishes children with putative dietary calcium-deficiency rickets from healthy children, consistent with increased vitamin D requirements in children with calcium-deficiency rickets. © 2010 American Society for Bone and Mineral Research

This descriptive population study of 307 public high school students, ages 15 to 17 years, was performed to establish reference ranges for orthostatic changes in heart rate and blood pressure in adolescents, and to identify influential variables. Noninvasive measurements of blood pressure and heart rate were obtained. Reference ranges for orthostatic heart rate change in this population at 2 minutes were –2 to +41 beats per minute and at 5 minutes were –1 to +48 beats per minute. Orthostatic blood pressure changes were within the adult range for 98% of adolescents tested. One-third of participants experienced orthostatic symptoms during testing. In conclusion, this study shows that orthostatic symptoms and large orthostatic heart rate changes occur in adolescents. This suggests that the current orthostatic heart rate criterion aiding the diagnosis of adult orthostatic intolerance syndromes is likely not appropriate for adolescents and should be reevaluated.

ABSTRACTObjective:To describe the relationships between gastric emptying, autonomic function, and postural tachycardia in adolescent patients with nausea and/or abdominal discomfort. It was hypothesized that patients with both gastrointestinal symptoms and symptoms of orthostatic intolerance are more likely to show abnormal tilt table results and delayed gastric emptying.Patients and Methods:A retrospective review was conducted of adolescent patients who came to a pediatric referral center because of nausea and dyspepsia and who subsequently underwent both autonomic reflex screening and gastric emptying testing. Patients with a heart rate change of 30 or more beats per minute on the heads‐up tilt table test were assigned to the postural orthostatic tachycardia syndrome (POTS) group (n = 21), and those with a heart rate change of fewer than 30 beats per minute on the heads‐up tilt table test were assigned to the non‐POTS group (n = 10).Results:There was no significant difference between the POTS and non‐POTS groups with regard to presenting symptoms (P > 0.05). Overall, 13 (42%) individuals had abnormal gastric emptying results (delayed in 6, accelerated in 7), but gastric emptying scores were similar between the POTS and non‐POTS groups. Furthermore, there was no correlation between an individual's gastric emptying results at 1, 2, and 4 hours and that person's heart rate change on HUT (r = −0.05, −0.15, and −0.19).Conclusions:Although altered gastric emptying and postural tachycardia are common in a referral population of adolescents with nausea and/or abdominal discomfort, the clinical presentation was not predictive of test results. Furthermore, delayed gastric emptying was not correlated with the current definition of postural tachycardia.

Abstract The incidence of distal forearm fractures peaks during the adolescent growth spurt, but the structural basis for this is unclear. Thus, we studied healthy 6- to 21-yr-old girls (n = 66) and boys (n = 61) using high-resolution pQCT (voxel size, 82 μm) at the distal radius. Subjects were classified into five groups by bone-age: group I (prepuberty, 6–8 yr), group II (early puberty, 9–11 yr), group III (midpuberty, 12–14 yr), group IV (late puberty, 15–17 yr), and group V (postpuberty, 18–21 yr). Compared with group I, trabecular parameters (bone volume fraction, trabecular number, and thickness) did not change in girls but increased in boys from late puberty onward. Cortical thickness and density decreased from pre- to midpuberty in girls but were unchanged in boys, before rising to higher levels at the end of puberty in both sexes. Total bone strength, assessed using microfinite element models, increased linearly across bone age groups in both sexes, with boys showing greater bone strength than girls after midpuberty. The proportion of load borne by cortical bone, and the ratio of cortical to trabecular bone volume, decreased transiently during mid- to late puberty in both sexes, with apparent cortical porosity peaking during this time. This mirrors the incidence of distal forearm fractures in prior studies. We conclude that regional deficits in cortical bone may underlie the adolescent peak in forearm fractures. Whether these deficits are more severe in children who sustain forearm fractures or persist into later life warrants further study.