Joumal of Intellectual Disability Research, 1992, 36, 251-257
Vitamin D status in children with Down's syndrome C. DEL ARCO,i J. A. RIANCHO,^ C. LUZURIAGA,^ J. GONZALEZ-MACIAS ^ & J. F L 6 R E Z ' Departments of 'Pharmacology, ^Medicine and ^Pediatrics, National Hospital 'M. de Valdecilla \ University of Cantabria, Santander, Spain ABSTRACT. The serum levels of the active Vitatnin D metabolites 25hydroxyvitamin D[25(OH)D], 1,25-dibydroxyvitamiti D[I,25(OH)2D] and 24,25 dihydroxyvitamin D I24,25(OH),D], were studied in 2t children with Down's syndrome (DS) in Cantabria, a northern region of Spain, located at 44''N latitude. Serum calcium, magnesium, phosphate, alkaline phosphatase, parathormonc and osteocalcine were also detemiined. In the DS group, the average values of the [hrce Vitamin D metabolites were comparable to those of an age-matched group both in winter and summer times. No child with DS showed values below the normal range, either in Vitamin D metabolites, or in the other parameters of calcium metabolism. The normal increment of 25(OH)D and 24,25(OH), values from .March to October was not observed infivechildren. This anomaly was corrected in three, after adequate rules of sun exposure during summer time v^ere followed. In the other two, the 25(OH)D levels were high throughout the study. This investigation shows that children with DS do not require Vitamin D prescription when appropriate periods of sunlight exposure are provided.
INTRODUCTION Vitamin therapy is one of a number of drug treatments that has been recommended for children with Down's syndrome (DS) over the years (Rynders, 1987, Pruess et al, 1989). The presumed effectiveness of this therapy is based on the idea that augmented concentrations of nutrients normally present in the human body are important for the treatment of 'mental disorders' (Pauling, 1968). Specific recommendations are usually given to include Vitamin D and other fatsoluble vitamins in several formulations prescribed to children with DS (Harrell et al, 1981), in spite of the fact that toxic effects of vitamin megadoses are increasingly recognized (Rudman & Williams, 1983). In contrast to previous reports that showed deficiencies in serum Vitamin A in DS individuals, recent studies using more elaborate assays have demonstrated that Vitamin A absorption in this condition is normal (Pueschel et al, 1990) and that hypercarotenaemia may even be present in some persons with DS (Storm, 1990). On the other hand, Cotrespondence: P}vfessor Jesus Fldrez, Department of Physiology and Pharmacology, University of Cantabria, Avda. Herrera Oria s/n, 39011 Santander, Spain.
251
252
C. delArco et al.
information on Vitamin D concentration and metabolism in children with DS is lacking, although an apparent hypersensitivity of DS children to vitamin D, leading to tissue calcification, has been reported (Schmid, 1982). The biological activity of Vitamin D depends first, on the previous exposure to ultraviolet radiation, and secondly, on subsequent hydroxylation processes which take place in the liver to form 25-hydroxyvitamin D [25(OH)D], and in the kidney to form 1,25-dihydroxyvitamin D [1,25(OH)2D]. 25(OH)D is the most abundant metabolite and its serum levels are considered to reflect the repletion status of the vitamin. 1,25(OH)2 D is the most active metabolite but circulates in much lower concentrations. Among other minor metabolites, 24,25 dihydroxyvitamin D [24,25(OH)T D ] may play some role in cartilage metabolism. Due to the various factors that might induce a reduction in the metabolism of Vitamin D in DS, such as intensity of sunlight exposure, failures in absorption and metabolism at the hepatic and renal levels, the present study was undertaken to determine the serum levels of these three metabolites in children with DS, and to compare them with those of normal and age-matched children in Cantabria, a northern region in Spain, located at 44° N latitude.
METHODS Subjects
Twenty-one children with DS who had a karyotype of trisomy 21 were randomly selected. There were 10 males and 11 males, and their ages ranged from 3 to 10 years. All were reared at home by their natural parents, and 19 out of 21 had attended early developmental programmes starting between 2 weeks and 3 years of age. The control group was formed by ambulatory children of similar ages who had disorders not affecting their general health status (e.g. strabismus, cryptorchidism and inguinal hernia). It is known that the serum level of some Vitamin D metabolites experiments seasonal variations which are related to changes in the solar radiation-induced synthesis of Vitamin D in the skin. Therefore, a preliminary study was first performed in control children to assess the monthly seasonal variations. Subsequently, two blood samples were drawn from children with DS at the months with the lowest and the highest values observed in the control group. All venous blood samples were obtained in the morning, after overnight fasting. None of the children were receiving Vitamin D supplements. Techniques
Vitamin D metabolites included those of Vitamin Dj and Vitamin D,. They were determined following the procedures of Reinhardt et al (1984) and Traba et al, (1984), conveniently modified to perform joint measurements of these metabolites in small serum samples (Del Arco et al, 1987; Riancho et al, 1988). Briefly, 1-2 ml of serum were extracted with acetonitrile and then chromatographed on sep-
Vitamin D in Down's syndrome children
253
pak cartridges (Waters, Milford, MA, USA). The extracts were subjected to high performance liquid chromatography (HPLC) on a silica column (Waters) using hexane/ethanol 95/5 (v/v) as the mobile phase. The eluate fractions containing the metabolites were separately collected and quantified by competitive protein binding. The source of binding protein was rat serum in the 25(OH)D and 24,25(OH).,D assays, and a receptor from calf thymus (m Inestar, Stillwater, MN, USA) in the 1,25(OH)^D assay. The overall interassay coeificients of variation were 11-4, 27-2 and 16-6% for 25(OH)D, 24,25(OH)2 and 2 respectively. Serum calcium, phosphate and alkaline phosphatase were measured by routine automatic methods. Serum parathormone (PTH) was determined by RIA with an antibody against the C-terminal region (m Inestar). Osteocalcin was also measured by RIA (M Inestar); magnesium by atomic absorption spectroscopy. The results are expressed as the mean±SD, unless otherwise indicated. The tijvotailed r-test was utilized in the analysis of statistical significance. RESULTS Serum levels of 25(OH)D in healthy children are shown on a monthly basis in Fig. 1. Levels in summer were consistently higher than in winter time, following the variation pattern of solar radiation. Compared to the radiation curve, there was a delay in the 25(OH) curve: the peak of sun radiation was attained in June and July, whereas that of 25(OH)D concentration appeared from July to October. The minimum level was observed in March (18-7+8-5 ng ml"') and the maximum in October (31-8±6-0 ng ml"'). Serum levels of 24,25(OH)2 D showed a similar,
o 500
o
30
CO
20
o
X
2 CM
11
200
40
~
X ^
—.
^
^1
10
CV1J
If)
c:^
0 Jan Feb Mar Apr May Jun Jul Aug Sep Oci Nov Dec
Figure 1. Serum concentrations of 25(OH)D (•) and 24,25COH)2D year in control children, in relation with sun radiation ( • ) .
through the
254
C. del Arco etal.
Table 1. Serum levels of Vitamin D metabolites in control children and children with Down's syndrome at different seasons (mean±SD) 25(OH)D (ngml"')
Control Down's Syndrome
Xpgml-.)
24,25(OH)2]D (ng ml-')
March
October
March
October
March
October
18-7±8-5
31-8±6-0*
50-0±16-9
47-2+7-5
1 -0±0-4
2-7±0-6*
20-2±5-6
32-9±8-l*
47-7±8-0
48-l±ll-l
1-4+0-6
*VaIues significantly higher than in March (P
Vitamin D status in children with Down's syndrome C. DEL ARCO,i J. A. RIANCHO,^ C. LUZURIAGA,^ J. GONZALEZ-MACIAS ^ & J. F L 6 R E Z ' Departments of 'Pharmacology, ^Medicine and ^Pediatrics, National Hospital 'M. de Valdecilla \ University of Cantabria, Santander, Spain ABSTRACT. The serum levels of the active Vitatnin D metabolites 25hydroxyvitamin D[25(OH)D], 1,25-dibydroxyvitamiti D[I,25(OH)2D] and 24,25 dihydroxyvitamin D I24,25(OH),D], were studied in 2t children with Down's syndrome (DS) in Cantabria, a northern region of Spain, located at 44''N latitude. Serum calcium, magnesium, phosphate, alkaline phosphatase, parathormonc and osteocalcine were also detemiined. In the DS group, the average values of the [hrce Vitamin D metabolites were comparable to those of an age-matched group both in winter and summer times. No child with DS showed values below the normal range, either in Vitamin D metabolites, or in the other parameters of calcium metabolism. The normal increment of 25(OH)D and 24,25(OH), values from .March to October was not observed infivechildren. This anomaly was corrected in three, after adequate rules of sun exposure during summer time v^ere followed. In the other two, the 25(OH)D levels were high throughout the study. This investigation shows that children with DS do not require Vitamin D prescription when appropriate periods of sunlight exposure are provided.
INTRODUCTION Vitamin therapy is one of a number of drug treatments that has been recommended for children with Down's syndrome (DS) over the years (Rynders, 1987, Pruess et al, 1989). The presumed effectiveness of this therapy is based on the idea that augmented concentrations of nutrients normally present in the human body are important for the treatment of 'mental disorders' (Pauling, 1968). Specific recommendations are usually given to include Vitamin D and other fatsoluble vitamins in several formulations prescribed to children with DS (Harrell et al, 1981), in spite of the fact that toxic effects of vitamin megadoses are increasingly recognized (Rudman & Williams, 1983). In contrast to previous reports that showed deficiencies in serum Vitamin A in DS individuals, recent studies using more elaborate assays have demonstrated that Vitamin A absorption in this condition is normal (Pueschel et al, 1990) and that hypercarotenaemia may even be present in some persons with DS (Storm, 1990). On the other hand, Cotrespondence: P}vfessor Jesus Fldrez, Department of Physiology and Pharmacology, University of Cantabria, Avda. Herrera Oria s/n, 39011 Santander, Spain.
251
252
C. delArco et al.
information on Vitamin D concentration and metabolism in children with DS is lacking, although an apparent hypersensitivity of DS children to vitamin D, leading to tissue calcification, has been reported (Schmid, 1982). The biological activity of Vitamin D depends first, on the previous exposure to ultraviolet radiation, and secondly, on subsequent hydroxylation processes which take place in the liver to form 25-hydroxyvitamin D [25(OH)D], and in the kidney to form 1,25-dihydroxyvitamin D [1,25(OH)2D]. 25(OH)D is the most abundant metabolite and its serum levels are considered to reflect the repletion status of the vitamin. 1,25(OH)2 D is the most active metabolite but circulates in much lower concentrations. Among other minor metabolites, 24,25 dihydroxyvitamin D [24,25(OH)T D ] may play some role in cartilage metabolism. Due to the various factors that might induce a reduction in the metabolism of Vitamin D in DS, such as intensity of sunlight exposure, failures in absorption and metabolism at the hepatic and renal levels, the present study was undertaken to determine the serum levels of these three metabolites in children with DS, and to compare them with those of normal and age-matched children in Cantabria, a northern region in Spain, located at 44° N latitude.
METHODS Subjects
Twenty-one children with DS who had a karyotype of trisomy 21 were randomly selected. There were 10 males and 11 males, and their ages ranged from 3 to 10 years. All were reared at home by their natural parents, and 19 out of 21 had attended early developmental programmes starting between 2 weeks and 3 years of age. The control group was formed by ambulatory children of similar ages who had disorders not affecting their general health status (e.g. strabismus, cryptorchidism and inguinal hernia). It is known that the serum level of some Vitamin D metabolites experiments seasonal variations which are related to changes in the solar radiation-induced synthesis of Vitamin D in the skin. Therefore, a preliminary study was first performed in control children to assess the monthly seasonal variations. Subsequently, two blood samples were drawn from children with DS at the months with the lowest and the highest values observed in the control group. All venous blood samples were obtained in the morning, after overnight fasting. None of the children were receiving Vitamin D supplements. Techniques
Vitamin D metabolites included those of Vitamin Dj and Vitamin D,. They were determined following the procedures of Reinhardt et al (1984) and Traba et al, (1984), conveniently modified to perform joint measurements of these metabolites in small serum samples (Del Arco et al, 1987; Riancho et al, 1988). Briefly, 1-2 ml of serum were extracted with acetonitrile and then chromatographed on sep-
Vitamin D in Down's syndrome children
253
pak cartridges (Waters, Milford, MA, USA). The extracts were subjected to high performance liquid chromatography (HPLC) on a silica column (Waters) using hexane/ethanol 95/5 (v/v) as the mobile phase. The eluate fractions containing the metabolites were separately collected and quantified by competitive protein binding. The source of binding protein was rat serum in the 25(OH)D and 24,25(OH).,D assays, and a receptor from calf thymus (m Inestar, Stillwater, MN, USA) in the 1,25(OH)^D assay. The overall interassay coeificients of variation were 11-4, 27-2 and 16-6% for 25(OH)D, 24,25(OH)2 and 2 respectively. Serum calcium, phosphate and alkaline phosphatase were measured by routine automatic methods. Serum parathormone (PTH) was determined by RIA with an antibody against the C-terminal region (m Inestar). Osteocalcin was also measured by RIA (M Inestar); magnesium by atomic absorption spectroscopy. The results are expressed as the mean±SD, unless otherwise indicated. The tijvotailed r-test was utilized in the analysis of statistical significance. RESULTS Serum levels of 25(OH)D in healthy children are shown on a monthly basis in Fig. 1. Levels in summer were consistently higher than in winter time, following the variation pattern of solar radiation. Compared to the radiation curve, there was a delay in the 25(OH) curve: the peak of sun radiation was attained in June and July, whereas that of 25(OH)D concentration appeared from July to October. The minimum level was observed in March (18-7+8-5 ng ml"') and the maximum in October (31-8±6-0 ng ml"'). Serum levels of 24,25(OH)2 D showed a similar,
o 500
o
30
CO
20
o
X
2 CM
11
200
40
~
X ^
—.
^
^1
10
CV1J
If)
c:^
0 Jan Feb Mar Apr May Jun Jul Aug Sep Oci Nov Dec
Figure 1. Serum concentrations of 25(OH)D (•) and 24,25COH)2D year in control children, in relation with sun radiation ( • ) .
through the
254
C. del Arco etal.
Table 1. Serum levels of Vitamin D metabolites in control children and children with Down's syndrome at different seasons (mean±SD) 25(OH)D (ngml"')
Control Down's Syndrome
Xpgml-.)
24,25(OH)2]D (ng ml-')
March
October
March
October
March
October
18-7±8-5
31-8±6-0*
50-0±16-9
47-2+7-5
1 -0±0-4
2-7±0-6*
20-2±5-6
32-9±8-l*
47-7±8-0
48-l±ll-l
1-4+0-6
*VaIues significantly higher than in March (P
