Endocrine glands thyroid

Adrenal gland weights were not affected in rats treated by gavage with 1,500 mg/kg/day trichloroethylene in com oil for 14 days (Berman et al. 1995). Histopathological changes in endocrine glands (thyroid, parathyroid, pancreas, adrenals, pituitary) have not been observed in rats or mice exposed by gavage to trichloroethylene in oil for intermediate or chronic durations (Maltoni et al. 1986 NCI 1976 NIP 1988, 1990). 

Nerve impulses stimulate the hypothalamus to send specific hormones to the pituitary gland, thus stimulating (or inhibiting) the release of tropic hormones. The anterior pituitary hormones in turn stimulate other endocrine glands (thyroid, adrenals, pancreas) to secrete their characteristic hormones, which in turn stimulate specific target tissues. 

The thyroid gland, located in the base of the neck, exerts i key role on growth and metabolism. In contrast with that of some of the other endocrine glands, this control is effected Ihrough a pair of relatively simple molecules, thyroxine, and its close congener, triiodothyronine. Cases of thyroid deficien-cy (hypothyroidism) are common enough to warrant the production... 

Thyroid gland. An endocrine gland that secretes thyroxin and triiodothyronine, hormones that modulate the rate of cellular metabolism. 

All OCPs are polytropic, parenchymatous poisons, afflicting the central nervous system, liver, kidneys, the heart muscle, the stomach and intestines, and the endocrine system (mostly the adrenal glands, thyroid, and ovaries). Morphological changes in warm-blooded creatures poisoned by OCPs vary from insignificant disruptions in circulation and reversible dystrophy to focal necroses these effects depend on the organism, the dose of OCP, how long the OCP remains active, as well as on other factors [9, 39, 40, A47, A79]. 

A trophic hormone acts on another endocrine gland to stimulate secretion of its hormone. For example, thyrotropin, or thyroid-stimulating hormone (TSH), stimulates the secretion of thyroid hormones. Adrenocorticotropin, or adrenocorticotropic hormone (ACTH), stimulates the adrenal cortex to secrete the hormone cortisol. Both trophic hormones are produced by the pituitary gland in fact, many trophic hormones are secreted by the pituitary. The pituitary gland is sometimes referred to as the "master gland" because its hormones regulate the activity of other endocrine glands. 

Endocrine Effects. Thyroid hyperplasia and pituitary cysts were observed in rats, but not mice, in a chronic bioassay study with endrin administered in the feed (NCI 1978). Treon et al. (1955) found diffuse degeneration of the adrenal glands in rats dosed with >1.25 mg/kg/day in their feed for 2 years however, the adrenal effects were absent at the 0.25 mg/kg/day dose. There has been no evidence of endocrine effects in occupationally exposed human populations. 

Thyroid Gland A highly vascular endocrine gland consisting of two lobes, one on either side of the trachea, joined by a narrow isthmus it produces the thyroid hormones which are concerned in regulating the metabolic rate of the body. [NIH]... 

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. 

Thyrotropin-releasing hormone is one of several small peptide hormones secreted by the anterior lobe of the pituitary gland. These are the master" hormones that function to stimulate hormone secretion from other endocrine glands. Thyrotropin stimulates the functioning of the thyroid gland. 

Location of major endocrine glands in humans. The hypothalamus regulates the anterior pituitary, which regulates the hormonal secretions of the thyroid, adrenals, and gonads (ovary in the female and testis in the male). 

Because of its anatomic prominence, the thyroid was one of the first of the endocrine glands to be associated with the clinical conditions caused by its malfunction. 

The hypothalamus-pituitary, thyroid, parathyroid, pancreas, adrenals, ovary, and testes are considered to be the principal endocrine glands producing hormones. A more complete list of the major endocrine hormones and their primary gland of origin is shown in Table 9.1. 

The endocrine glands such as the thyroid, the pituitary gland, and the pineal gland, are extremely sensitive to fluoride and accumulate aluminum. 

Mariotti S (2002) Normal Physiology of the Hypothalmic-Pituitary-Thyroidal System and Relation to the Neural System and Other Endocrine Glands. [Internet resource] http //www.thyroidmanager.org/Chapter4/4-frame.htm Meinhold H, Altmann R, Bogner U, Finke R, Schleusener H (1994) Evaluation of various immunometric TSH assays. Exp Clin Endocrinol 102 23-26 Oda Y, Sanders J, Roberts S, Maruyama M, Kato R, Perez M, Petersen VB, Wedlock N, Furmaniak 1, Smith RB (1998) Binding characteristics of antibodies to the TSH receptor. J Mol Endocrinol 20 233-244... 

Figure 13.1 Major human endocrine glands (1) pineal gland, (2) pituitary gland, (3) thyroid gland, (4) thymus, (5) adrenal gland, (6) pancreas, (7) ovary and (8) testes.

Hormones synthesised by the antei ior pituitary that regulate the activity of various endocrine glands are referred to as tropic hormones (e.g. thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), follicle-stimulating hormone (FSH)). 

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