Alterations in serum levels

Additional studies could characterize thyroid effects of PBDEs in humans and develop specific correlations between levels and duration of exposure and alterations in serum levels of T4. 

Shimazu E, Hashimoto K, Okamura N, Koike K, Komatsu N, Kumakiri C, Nakazato M, watanabe J, Shinoda N, OkadaS, lyo M (2003) Alterations in serum levels of brain-derived neurotrophic factor (BDNF) in depressed patients with or without antidepressant. Biol Psychiatry 54 70-75. 

Available intermediate- and chronic-duration oral studies in animals indicate that the thyroid and liver are the main systemic targets of PBDE toxicity as shown by effects mainly including enlargement and histological alterations in both organs and changes in serum levels of thyroid hormones. Several acute-duration studies of pentaBDE suggest that immunosuppression may also be an important health end point. Very little information is available on potential neurotoxic effects of PBDEs, mainly the results of three... 

A potential biomarker of exposure to PBDEs relates to their effect on the thyroid gland. As discussed in Sections 3.2.2.2, Endocrine Effects, thyroid changes in rats and mice include reduced serum thyroxine (T4) levels w itli no changes in scrum TSH (Damerud and Sinjari 1996 Fowles et al. 1994 Hallgren and Damemd 1998 WIL Research Laboratories 1984 Zhou et al. 2001, 2002). Additional studies are needed to characterize thyroid effects of PBDEs in humans and develop specific correlations between levels and duration of exposure and alterations in senun levels of T4. This potential biomarker is not specific to PBDEs because PBBs and other antithyroid agents can have similar effects. 

In summary, CDDs were shown to alter endocrine parameters mostly in rodent studies. One of the better characterized effects was a decrease in serum T4, caused apparently by CDD-induced T4 metabolism and excretion. Alterations in T3 levels were less consistent. Results from additional studies suggested that... 

A number of reproductive effects, including decreased fertility, damage to the gonads, and alterations in hormone levels, have been observed in male and female animals orally exposed to 2,3,7,8-TCDD. In male rats, a dose- and time-dependent reduction of serum testosterone and dihydrotestosterone levels was observed after acute oral exposure to 2,3,7,8-TCDD (Mebus et al. 1987 Moore et al. 1985, 1991). Furthermore, male rats had decreased weight of seminal vesicles following oral exposure to... 

No significant alterations in serum T4 or TSH levels or correlations with selenium intake were found. 

The literature contains many reports about changes in serum tryptophan levels in patients with a variety of illnesses. In some cases, investigators have attached much significance to these alterations in serum tryptophan levels. However, at present, in most cases it is difficult to interpret the significance of these findings. Yet one should be aware of correlations between certain diseases and serum tryptophan levels. It is appropriate to cite some examples of diseases where serum tryptophan levels have been found to be diminished or increased. 

From 1952 to 1962, several experimental studies using rats fed a choline-deficient diet reported the development of aortic arteriosclerosis.171-173 Using rats fed a choline-deficient diet, Sidransky et al.174 reported that elevated (2%) dietary tryptophan affected the elevated serum lipid levels of rats fed the choline-deficient diet for 1 week. Within 1 week the added dietary tryptophan to the choline-deficient diet caused a return in serum cholesterol, HDL cholesterol, and triglyceride values to levels present in rats fed the choline-supplemented diet. The significance of the alterations in serum lipids due to added dietary tryptophan was unknown, but it stressed that a specific amino acid (L-tryptophan) excess created a further nutritional imbalance, which could influence the altered circulating serum lipids due to choline deficiency. The alterations in serum lipid due to choline deficiency were thought to influence the development of arteriosclerosis in the rat, and possibly the added dietary tryptophan was able to prevent the effect. Further experimental studies are needed to determine whether this speculation was valid. 

Sidransky and Verney5 reported that cycloheximide added in vitro diminished 3H-tryptophan binding to hepatic nuclei, probably related to its structural effect on the nuclear receptor. This effect may also occur in vivo, in addition to cycloheximide s action in inhibiting tissue and organ protein synthesis, and may possibly contribute in a minor way to the alteration in tryptophan level in serum. 

I. Pharmacology. Potassium is the primary intracellular cation, which is essential for maintenance of acid-base balance, intracellular tonicity, transmission of nerve impulses, contraction of cardiac, skeletal, and smooth muscle, and maintenance of normal renal function (and ability to alkalinize urine). Potassium also acts as an activator in many enzyme reactions and participates in many physiological processes such as carbohydrate metabolism, protein synthesis, and gastric secretion. Potassium is critical in regulating nerve conduction and muscle contraction, especially in the heart. A variety of toxins cause alterations in serum potassium levels (see Table 1-27, p 38). 

In a study in healthy subjects, enoxacin did not appear to alter phenytoin serum levels, nor were multiple-dose serum enoxacin levels significantly altered by phenytoin. ... 

This reduction in phenytoin levels by phenobarbital has been described in other reports. " However, some of these also described a very transient and small rise or no alteration in serum phenytoin levels in individual patients. Three other studies have found that phenobarbital does not alter phenytoin levels. " ... 

Contrasting with these reports is a study in 12 schizophrenic patients, which found that the addition of risperidone to clozapine was both effective and well tolerated, although 4 patients complained of mild akathisia. Serum clozapine levels were not significantly changed. A retrospective study in 18 patients also found that risperidone did not alter clozapine serum levels. ... 

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