Normal serum levels

Folic acid appears in the plasma approximately 15 to 30 minutes after an oral dose peak levels are generally reached within 1 hour. After IV administration, the drug is rapidly cleared from the plasma. Folic acid is metabolized in the liver. Normal serum levels of total folate have been reported to be 5 to 15 ng/mL normal CSF levels are approximately 16 to 21 ng/mL. In general, folate serum levels less than 5 ng/mL indicate folate deficiency, and levels less than 2 ng/mL usually result in megaloblastic anemia. A majority of the metabolic products appeared in the urine after 6 hours excretion was generally complete within 24 hours. 

Contraindications Active hepatic disease diabetic ketoacidosis increased serum transaminase levels, including ALT greater than 2.5 times normal serum level type 1 diabetes mellitus... 

Patients with severe atrophic gastritis may have impaired absorption of vitamin B12 and a reduced serum level of the vitamin, but this is not accompanied by either megaloblastic anemia or neuropathy. Parietal-cell antibodies have been found in 33% of patients with gastritis, none of these patients having pernicious anemia (12, V4). Intrinsic factor antibodies were not found, and this was not surprising since it is rare to find antibodies to intrinsic factor in the absence of pernicious anemia. Patients with superficial gastritis usually have normal vitamin B12 absorption and normal serum levels of the vitamin. 

Vitamin D that is taken up by the fiver is converted to 25-hydroxyvitamin D by a microsomal hydroxylase (Fig. 30-3). 25-Hydroxyvitamin D is the main circulating form of vitamin D in the serum and the best indicator of vitamin D status. Normal serum levels are 14-60 ng/mL (35-150 nmol/L). When serum calcium concentrations decline, 25-hydroxyvitamin D is converted to 1,25-dihydroxyvitmin D by la-hydroxylase, a mixed-function oxidase that is located in the inner mitochondrial membrane in kidney tissue and whose expression is regulated by parathyroid hormone (PTH). The main function of 1,25-dihydroxyvitamin D is to increase the intestinal absorption of dietary calcium and phosphorus. When serum concentrations of calcium and phosphorus are normal or when large doses of vitamin D are administered, 25-hydroxyvitamin D is metabolized to 24,25-dihydroxyvitamin D in the renal... 

Plasma levels of cytokines were measured in subjects hospitalized with nephropathia epidemica. Concentrations of TNFa, IL-6, and IL-10 were increased in ail of these patients at admission. TNFa concentrations were still increased 1 week after onset of disease levels of IL-6 and IL-10 normalized. Serum levels of tlie two soluble TNF receptors p55 and... 

Since the dominant subclass is IgG, and IgG2 and IgG4 behave similarly, these set the overall apparent catabolism of IgG. With a normal serum level (1000 mg/100 ml), the FCR is 6-7% and the is 22 days. If the level is lowered below 100 mg/100 ml in an otherwise normal subject, the FCR becomes 2% and the lengthens to 60 days. This is of value in replacement treatment of hypogammaglobulinemia due to inadequate synthesis of IgG. With elevation of the serum level, the FCR rises to a maximum of 18% when the normal mechanism protecting IgG from catabolism becomes saturated, at about 2500 mg/100 ml and above, shortening the to 10-13 days. This means that, when a myeloma IgG is reduced from 2.4 1.8 g/100 ml, a substantial decrease (some 40%) in IgG production has been achieved with a similar reduction from 240 to 180 mg/100 ml, however, decreased synthesis of only some 20% has occurred. A model to explain this phenomenon has been proposed (B22) and modified (Rll). 

Estimates of the daily catabolism of IgA vary from 0.6 g (G7) to 2 g (S17), mainly because of different estimates of the normal serum level, as all workers agree on a of about 6 days. It also appears that the degree of I labeling may have a bearing on how much IgA can enter the lamina propria pools (see Section 3.3) and become dimerized for secretion. The absolute total daily synthesis is thus not clear (probably 1.5 g), but the 7S IgA of the serum is distributed similarly to IgG and has an FOR of 40%. Thus even the increased catabolism of protein-losing enteropathy increases the FCR only to 60%, and the serum level rarely if ever falls below the 2 SD lower limit of normal. Subnormal IgA levels are therefore almost always due to impaired synthesis. It is of interest to note here that subjects born without IgA, presumably sensitized by breast-feeding or kissing, often develop antibodies to IgA and thereby show increased catabolism and occasionally reactions to administered IgA (S32). 

The diagnosis of D-lactic acidosis is suspected in patients with disorders of the small intestine causing malabsorption and when the serum anion gap (Chapter 39) is elevated in the presence of normal serum levels of L-lactate and other organic acids. Measurement of serum D-lactate requires special enzymatic procedures utilizing D-lactate dehydrogenase and NADH. As D-lactate is converted to pyruvate, NADH is oxidized to NAD+ which is detected spectrophotometrically (Chapter 8). 

Hepatic Effects. Workers exposed chronically to 0.01-0.5 mg/m of vanadium dusts had normal serum levels of four enzymes (serum alkaline phosphatase, alanine amino- transferase, aspartate aminotransferase, and lactate dehydrogenase) that are commonly used to detect possible liver damage (Kiviluoto et al. 1981a). 

Ohmi and Arias have investigated the plasma levels of alpha-class GST in hepatocellular carcinoma in the rat and humans (03). They found that serum ligandin concentrations rose progressively following the transplantation of a lig-andin-containing rat hepatocellular carcinoma in rats or athymic mice. The mean serum ligandin concentrations within 4 months exceeded normal serum levels by a factor of 10. When serum ligandin concentrations were studied in humans it was reported that levels were Increased in 11 of 15 patients with primary hepatocellular carcinoma. Normal levels were found in 19 of 22 patients with primary carcinomas without hepatic involvement. 

Substance Interfering level (mg dr ) Normal serum level (mgdl- )... 

Whole blood, serum and blood cells have been analyzed for Mn by many workers using furnace methods, although contamination has probably produced large errors in many of these studies. The normal serum level is close to 1 fig/U probably lower (Versieck and Cornells, 1980). We recommend that serum be diluted 1 + 2 in the matrix modifier and 0.2% Triton X-100 and 20-/detection limit of about 0.1 /ig/L. The same methods have been used for urine (Freeh et al., 1985). 

Levothyroxine (T4) (e.g., Synthroid) Replaces normal serum levels of T4 and T3 (T4 is converted into T3 by deiodination in the periphery). Drug of choice for hypothyroidism. No toxicity at replacement concentration. Overdose causes hyperthyroid effects (top of page). 

Enteral absorption of sodium levothyroxine is about 80% in an empty stomach. T4 plasma half life is long (7 days), because of plasma protein binding. Levothyroxine administration provides normal serum levels of both T4 and T3, the latter by 5 -monodeiodination of T4 in the peripheral tissues (Vanderpump et aL, 1996). 

Subclinical or mild hypothyroidism is defined by normal serum levels of T4 and T3, with mildly elevated serum... 

Mesquita J, Cepa S, Silva L, Machado A. Lithium toxicity at normal serum levels. J Neuropsychiatry Clin Neurosd 2010 22(4) E29. 

Low cerebrospinal fluid (CSF) levels of vitamin B12 and folate in dementia patients with normal serum levels have been demonstrated in a number of studies. Hence, CSF vitamin B and folate may be more sensitive indicators of their deficiencies at tissue level. This can be due to formation of inactive vitamin analogues at tissue level which are not detected by current analytical methods and disturbed transport of vitamin across the blood-brain barrier. 

The retinopathy may be related to vitamin A or carotenoid deficiency (Salt et al. 1960, and others), and low serum levels of vitamin A were found by Campbell and Tonks (1963) in other patients with retinitis pigmentosa. However, in the patient of Salt et al., normal serum levels of this vitamin were maintained from the age of 22 months by the administration of water-soluble vitamin A preparations and he nevertheless showed the first signs of retinitis pigmentosa at the age of 5 years (Wolff et al. 1966). Similarly Forsyth et al. (1965) administered vitamin A to their patients in daily doses of 20,000 to 40,000 lU, and achieved serum levels of 55 lU/lOOml (normal 72 lU/lOOml) but were unable to prevent the development of retinitis and the appearance of neurological signs at the age of 7. Even with normal serum levels of vitamin A, its transport to important sites may not be secured, and coupling with j8-lipoproteins may be necessary for its action. In addition, some cells may need carotenoids which are almost completely absent in the serum of a-j8-lipoproteinemic patients. 

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