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Biomedical subjects

T Markestad

Publications and source records attributed to T Markestad.

At least 91 records · Page 5Linked to original sources
PubMed1989

Serum concentrations of vitamin D metabolites in rachitic Libyan children.

Twenty-two consecutive patients with rickets were studied in Benghazi, Libya. All were less than 2 years old. Rickets was associated with traditional cultural habits that limited sunshine exposure of the mothers and their infants, and with breast-feeding. Serum concentrations of the vitamin D metabolites 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D, and 24,25-dihydroxyvitamin D, and other parameters of mineral metabolism were typical of vitamin D deficiency disease, as was the biochemical and clinical response to treatment. Minimum safe serum levels of 25-OHD (20 nmol/L), and the serum levels of vitamin D metabolites in response to vitamin D treatment, were identical to previously obtained results from native Norwegian and Norwegian immigrant children with rickets, suggesting lack of racial differences in response to vitamin D. Fifty percent of the patients had adequate levels of vitamin D metabolites at the time of diagnosis, indicating that they had recently received oral vitamin D or cutaneous exposure to sunshine. Many cases of rickets in the area may, therefore, be spontaneously cured when the children's maturity allows adequate mobility and independence to achieve exposure to sunshine.

Breast Feeding↗
PubMed1989

Preliminary results from the Collaborative Alabama and Scandinavian Study of Successive Small-for-Gestational Age Births.

The study "Successive Small-for-Gestational Age Births" (SGA study) was initiated and is sponsored by the National Institutes of Health (N.I.H.) in the U.S.A. Its purpose is to describe and characterize the different types of intra-uterine growth retardation and their consequences, to assess the associated risk factors, and to provide a basis for preventive measures. Starting in 1986, it runs concurrently in Bergen and Trondheim (Norway), Uppsala (Sweden) and Birmingham, Alabama (U.S.A.), recruiting pregnant para 1 and 2 mothers at high risk of having an SGA birth and a random (control) sample of the total pregnant population. Data collection will end in late 1989, when the last-born children have reached 13 months of age. At the present symposium, investigators from all four study centers and the N.I.H. described the study design and discussed problems of methodology. Strict standardization of parameters to determine gestational age (ultrasound, menstrual dates) is a prerequisite for comparison of results over time and between study centers. Some preliminary results were presented.

Alabama↗
PubMed1987

Intermittent high-dose vitamin D prophylaxis during infancy: effect on vitamin D metabolites, calcium, and phosphorus.

In infants receiving intermittent high dose vitamin D prophylaxis (600,000 IU ergocalciferol per dose orally) every 3-5 mo, the serum concentrations of vitamin D metabolites, calcium (Ca), and phosphorus (P) were determined before and 2 wk after each dose. The 25-hydroxyvitamin D (OHD) concentrations increased to well above normal but the values returned to the normal range before each subsequent dose. The 24,25- and 25,26-dihydroxyvitamin D ([OH]2D) levels followed a pattern similar to that of 25-OHD, and both were closely related to the latter (r = 0.85, p less than 0.005, and r = 0.84, p less than 0.005, respectively). The 1,25-(OH)2D concentrations did not vary in a consistent pattern and remained largely within the normal range. All infants had normal Ca levels before the first dose but 14 infants (34%) later had one or both Ca values above the upper normal limit of 2.80 mmol/L (2.81-3.32 mmol/L), indicating that the vitamin D doses were excessive despite the lack of accumulative increases in serum vitamin D concentrations.

24,25-Dihydroxyvitamin D 3↗
PubMed1986

Plasma concentrations of vitamin D metabolites in pubertal girls with anorexia nervosa.

Plasma concentrations of 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D (1,25-(OH)2D), 24,25-dihydroxyvitamin D (24,25-(OH)2D) and vitamin D-binding protein (DBP) were measured in 12 pubertal girls (aged 10-18 yr) with anorexia nervosa in relapse. The results were compared with similar data obtained in 81 healthy girls representing all stages of puberty. The patients with anorexia nervosa had significantly lower 1,25-(OH)2D levels (71 vs. 124 pmol/l; p less than 0.0005), and significantly higher 24,25-(OH)2D levels (6.0 vs. 3.2 nmol/l; p less than 0.0005), whereas the 25-OHD concentrations were similar in the two groups (85.7 vs. 86.7 nmol/l). The molar ratios of 24,25-(OH)2D to 25-OHD, which reflects the relative activity of the 24-hydroxylation, were significantly higher in the anorectics (6.6% vs. 3.6%; p less than 0.0005). The mean level of DBP did not differ between the two groups, and accordingly the calculated "free-fraction of 1,25-(OH)2D" was significantly lower in the anorectic patients (p less than 0.0005). It appears that the regulatory mechanisms of the vitamin D endocrine system are altered in the patients with anorexia nervosa at puberty resulting in a relative decrease of the plasma concentration of 1,25-(OH)2D and increase of the 24,25-(OH)2D concentration.

24,25-Dihydroxyvitamin D 3↗
PubMed1986

Serum concentrations of vitamin D metabolites in vitamin D supplemented pregnant women. A longitudinal study.

The serum concentrations of the vitamin D metabolites 25-OHD, 1,25-(OH)2D, 24,25-(OH)2D and 25,26-(OH)2D, and of vitamin D binding protein (DBP), were determined longitudinally in 22 vitamin D supplemented pregnant women, and in 17 age-matched non-pregnant women studied during the summer. The pregnant women had higher 25-OHD and 1,25-(OH)2D, similar 24,25-(OH)2D, and lower 25,26-(OH)2D concentrations than the non-pregnant group. The relative concentrations of 24,25-(OH)2D and 25,26-(OH)2D (expressed as the molar ratio of these metabolites to 25-OHD) were lower during pregnancy. The DBP levels were increased in pregnancy, but the calculated free fraction (i.e. not bound to DBP) of the hormonal form of vitamin D, 1,25-(OH)2D, was still persistently higher in the pregnant than in the non-pregnant women. The study suggests that a daily vitamin D supplement of 400 IU satisfies the vitamin D requirement of pregnant women living in a cool climate with limited sun exposure. The increased absolute and relative concentration of 1,25-(OH)2D and decreased relative levels of 24,25-(OH)2D and 25,26-(OH)2D further suggest that the increased intestinal calcium and phosphate absorption, which is known to occur during pregnancy, is at least partially mediated by the vitamin D endocrine system.

24,25-Dihydroxyvitamin D 3↗
PubMed1985

Plasma concentrations of vitamin D metabolites during puberty of diabetic children.

Plasma concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, 24,25-dihydroxyvitamin D and vitamin D binding protein were determined in 87 serum samples from 46 Type 1 (insulin-dependent) diabetic children and adolescents at the various stages of puberty. The results were compared with data similarly obtained from healthy pubertal children. The diabetic patients had lower mean 1,25-dihydroxyvitamin D concentrations (p less than 0.05) and higher molar ratios of 24,25-dihydroxyvitamin D to 25-hydroxyvitamin D (p less than 0.05) than their healthy counter parts. In contrast to the reference group, the diabetic patients failed to attain the increase in 1,25-dihydroxyvitamin D normally seen during the pubertal stages of maximal growth velocity. The mean plasma levels of vitamin-D binding protein did not differ between the two groups, and a calculated 'free' 1,25-dihydroxyvitamin D value followed a pattern similar to that of total 1,25-dihydroxyvitamin D throughout puberty for both groups. The results suggest that the regulatory mechanisms of the vitamin D endocrine system are altered in diabetic children at puberty, resulting in a relative decrease in 1,25-dihydroxyvitamin D plasma concentration and increased 24,25-dihydroxyvitamin D levels.

24,25-Dihydroxyvitamin D 3↗
PubMed1985

Vitamin D deficiency rickets and vitamin B12 deficiency in vegetarian children.

During the years 1978-83 four vegetarian children have been admitted to the pediatric departments of Ullevaal and Aker Hospitals in Oslo and Haukeland Hospital, Bergen, with the diagnosis of vitamin D deficiency rickets. One had vitamin B12 deficiency as well. All had been fed a vegetarian diet with some cows' milk, but without vitamin supplementation. All had marked hypocalcemia, and three had tetany or convulsions. All responded well to conventional doses of vitamin D therapy. Two of the mothers had vitamin D deficiency, and one of them also had vitamin B12 deficiency. This report describes the case histories of these children, and also discusses predisposing factors of vegetarian diets for the development of nutritional rickets.

Child Nutritional Physiological Phenomena↗
PubMed1984

Anticonvulsant drug therapy in human pregnancy: effects on serum concentrations of vitamin D metabolites in maternal and cord blood.

Serum concentrations of the main vitamin D metabolites and of calcium, phosphate, and alkaline phosphatase were determined in each of the three trimesters of pregnancy and in simultaneously obtained maternal and cord blood at delivery in 22 epileptic women treated with diphenylhydantoin or carbamazepine alone or with a combination with one other drug. The results were compared with similarly obtained data from 22 normal pregnancies. Women in both groups received supplements of 400 IU vitamin D3 per day. All the women had 25-hydroxyvitamin D levels within the normal range for healthy adults (greater than 12 ng/ml) throughout pregnancy. The epileptic women had, however, significantly (p less than 0.05) lower median 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels and higher median 25,26-dihydroxyvitamin D values than the reference group. The 24,25-dihydroxyvitamin D concentrations did not differ significantly, but the median ratio of 24,25-dihydroxyvitamin D to 25-hydroxyvitamin D was higher in the epileptic women at the end of pregnancy (p = 0.05). The respective differences in cord serum concentrations reflected those of the mothers at delivery. Serum calcium tended to be lower during epileptic pregnancy, but none were hypocalcemic. The alkaline phosphatase and phosphate values did not consistently differ from those of the reference women. The median alkaline phosphatase level of cord serum was slightly higher in the epileptic group, but the calcium and phosphate levels were similar to the reference values. The various biochemical parameters of the carbamazepine-treated women tended to be intermediate between those of the healthy and diphenylhydantoin-treated groups. Antiepileptic drug therapy appears to affect vitamin D metabolism and calcium homeostasis during pregnancy. The derangements may not be of major clinical significance, however, in vitamin D-supplemented and normally functioning women on long-term low-dose therapy.

24,25-Dihydroxyvitamin D 3↗