Thiamine normal range

The within-assay and between-assay coefficients of variation for the determination of total thiamine in whole blood were 4.2% and 4.4%, respectively. The between-assay analytical recovery of TPP added to blood samples was 99.9 11.7% (mean SD). The analysis of samples from 98 normal volunteers, not matched for age and sex, revealed an overall range for total thiamine of 70 to 185 nmol/L blood, with a mean value of 115 mnol/L blood. The frequency distribution of total thiamine in these blood samples is shown in Figure 5 a normal range of total thiamine 95 to 155 nmol/L blood was obtained (25). Schrijver extended the number of analyses of total thiamine in whole blood to 598 normal volunteers and obtained a value of 129.2 21.9 nmol/L blood (personal communication). This HPLC method could also be applied to the analysis of thiamine in plasma and erythrocytes. 

In an investigation of the water-soluble vitamins in human skin,71 it was found that 15 individuals showed relatively small ranges (less than 2-fold) for vitamin B12, folic acid, and biotin about 2-fold ranges in the cases of riboflavin, niacin, and thiamine about a 4-fold range in the case of ascorbic acid, and more than a 5-fold range in the case of pantothenic acid. In another study72 it was found that the total choline content of normal skin varied in four individuals over approximately a 10-fold range 127 to 1200 ig. per gm. The variation in the free choline in the same individuals was relatively small. 

The dietary requirement for thiamine is proportional to the caloric intake of the diet and ranges from 1.0 - 1.5 mg/day for normal adults. If the carbohydrate content of the diet is excessive then an increased thiamine intake will be required. Requirement is increased in pregnancy and lactation. It also depends of intestinal s)mthesis and absorption and fat content of diet (increased Pyruvate). 

The most reliable method for assessing thiamin status involves the measurement of red blood cell transketolase. This enzyme is measured with and without the addition of TPP to the enzyme assay mixtures. In dietary thiamin deficiency, synthesis of transketolasc continues, but conversion of the apoet zyme to the holoenzyme in the cell is inhibited, resulting in the accumulation of the enzyme in the apoenzyme form. Addition of TPP to cell homogenates results in the conversion of apoenzyme to holoenzyme. This conversion can easily be detected by enzyme assays. The amount of shmulation of enzyme activity by the added TPP is used to assess thiamin status. A deficiency is indicated by a shmulation of over 20%, The TPP-dependent stimulation, using red blood cells from normal subjects, ranges from 0 to 15%. 

A young man developed marked deterioration in his vision and oscillating vision, despite normal optic fundi, during parenteral nutrition he went on to develop a characteristic Wernicke s encephalopathy, confirmed by characteristic findings on MRI brain scan (42). The serum vitamin Bi concentration was 110 pg/ml (reference range 200-500). He responded fuUy to thiamine 300 mg/day in addition to betamethasone for 4 weeks. 

Percentage stimulation [i.e. 100 x (saturated/unsaturated)] is referred to as the TDP effect. Based on the majority of the literature, normal thiamine is associated with 0-15% stimulation, moderate thiamine deficiency with 16-24% stimulation, and severe thiamine deficiency with more than 25% stimulation (Table 16.1). Studies of healthy control individuals report average TDP effects as low as 3.0 4.7 (Kawai et al. 1980) to as high as 17 12.3% (Lu and Frank 2008) with a range of intermediate results (Boni et al. 1980 Kuriyama et al. 1980 O Rourke et al. 1990). 

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