Hormone levels

Increased hormonal levels have resulted in better mminant animal performance. Fstrogen-containing compounds, eg, zearalenone [17924-92-4], 18 22 5 available to improve growth and feed efficiency. These estrogens are given as ear implants. Melengestrol acetate [2919-66-6] (MGA),... 

Fig. 1. Mechanisms controlling free thyroid-hormone levels.

Peripheral Antagonists. The relatively long duration of action of the thyroid hormones makes it desirable to have compounds capable of blocking them competitively at their site of action. This is desirable in the treatment of thyroid storm where the reduction of circulating hormone levels brought about by the inhibition of their synthesis is too slow. 

PCBs and dioxins are well known for their ability to induce certain iso-enzymes of P450 in the mammalian liver. Some of these iso-enzymes are involved in the metabolism of steroids, and it is possible that changes in rates of metabolism might disturb hormone levels. 

Toxicants that alter circulating steroid hormone levels... 

Disruption of thyroid functions in vertebrates has been suggested to constitute a potential threat to many vital functions. For example, there is a possibility that disruption to the thyroid hormone levels during embryogenesis could result in disturbed behaviour patterns in the adult form, possibly interfering with migration in certain species and sonar functions in cetaceans. In anurans, thyroid hormones are essential for initiating metamorphosis. ... 

Periodic testing of growth hormone levels, glucose tolerance, and thyroid functioning may be done at intervals during treatment. 

In vivo studies in animals suggest that endosulfan may disrupt normal reproductive hormone levels in male animals, but that it is not an endocrine disrupter in females. Persistent depressed testicular testosterone was seen in male rats after intermediate duration oral exposures to endosulfan. In ovariectomized female rats, orally administered endosulfan did not induce normal development of female reproductive tissues, and in female mice and immature female rats, acute parenteral exposure to endosulfan did not affect several endocrine-related end points. In vitro studies have evaluated endosulfan for estrogen receptor (ER) and cytosolic protein binding affinity, ER-mediated reporter gene expression, estrogenic induction of cell proliferation, and alteration of relative abundance of active estradiol metabolites. Overall, in vitro evidence in favor of endosulfan estrogenicity indicates relatively weak potency compared to 17[3-estradiol. Apparently contradictory results were reported in different... 

The overall evidence indicates that endosulfan administered in vivo may be disruptive of reproductive hormone levels in male animals. On the other hand, endosulfan is neither estrogenic nor disruptive of thyroid or pituitary hormone levels in females in vivo, despite its weak estrogenicity in several in vitro test systems. 

Darnerud, P.O., Morse, D.C., Klasson-Wehler, E. et al. (1996). Binding of 3,3, 4,4 TCB metabolite to fetal transthyretin and effects on fetal thyroid hormone levels in mice. Toxicology 106, 105-114. 

Kuriyama, S.N., Wanner, A., and Fidalgo-Neto, A.A. (2007). Developmental exposnre to low-dose PBDE-99 Tissue distribution and thyroid hormone levels. Toxicology 242, 80-90. 

ICHIKAWA T (1974) Administration of gamma oryzanol to women suffering from postmenopausal syndrome. Changes of hormone levels before and after administration. J New Drugs Clinics, 23 40. 

Thyroid function tests abnormal thyroid hormone levels may suggest hypo- or hyperthyroidism, either of which may be associated with constipation. 

Cl8. Christeff, N Auclair, M. C., Benassayag, C., Carli, A., and Nunez, E. A., Endotoxin-induced changes in sex steroid hormone levels in male rats. J. Steroid Biochem. 26,67-71 (1987). 

R6. Richmand, D. A., Molitch, M, E., and O Donnell, T. E, Altered thyroid hormone levels in bacterial sepsis The role of nutritional adequacy. Metabolism 29,936-939 (1980). 

R16. Ross, R., Miell, J., Freeman, E Jonest, J., Matthews, D., Preece, M and Buchanan, C, Critically ill patients have high basal growth hormone levels with attenuated oscillatory activity associated with low levels of insulin-like growth factor-I. Clin. Endocrinol. 35,47-54 (1991). 

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