Hormone concentration effects

HABiTO R c, MONTALTO J, LESLIE E, BALL M J (2000) Effects of replacing meat with soyabean in the diet on sex hormone concentrations in healthy adult males. 84 557-563. 

Mechanism of Action A dopamine agonist that directly stimulates dopamine receptors in the corpus striatum and inhibits prolactin secretion. Also suppresses secretion of growth hormone. Therapeutic Effect Improves symptoms of parkinsonism, suppresses galactorrhea, and reduces serum growth hormone concentrations in acromegaly. 

The hormone concentration necessary for the binding and activation of a receptor dimer can be very different for the various dimers. The available hormone concentration in a particular cell type thus plays an important role in receptor activation. The effective intracellular concentration of a hormone is furthermore subject to a diverse regulation mechanism (see 4.1). 

Figure 13.8. Effects of route and sustained release formulation on the time course of human growth hormone concentration in plasma. Shown is the average time course of human growth hormone (hGH) in plasma after intravenous (0.02mg/kg) and subcutaneous (0.1 mg/kg) administration in humans. Arrows indicate weekly subcutaneous dosing of hGH in solution. A single dose of the same protein formulated in polylactide-co-glycolide (PLG) microspheres (0.75 mg/kg) given subcutaneously sustains human growth hormone levels in plasma for at least one month.

In 50 women taking levothyroxine either for primary thyroid failure or for hypothyroidism secondary to radioiodine treatment for hyperthyroidism, there was no difference between the two groups in terms of bone density at the hip or spine and no difference from the reference population (31). In addition, there was no correlation between bone density and circulating thyroid hormone concentrations or duration of levothyroxine replacement. These findings are reassuring, although large studies of fracture risk are required, in view of previous evidence of an adverse effect of levothyroxine on bone mineral density, especially in post-menopausal women (32). 

Pluim HJ, deVijlder JJM, Olie K, et al. 1993c. Effects of pre and postnatal exposure to chlorinated dioxins and furans on human neonatal thyroid hormone concentrations. Environ Health Perspect 101 504-508. 

Seo B-W, Li M-H, Hansen LG et al. 1995. Effects of gestational and lactational exposure to coplanar polychlorinated biphenyl (PCB) congeners or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on thyroid hormone concentrations in weanling rats. Toxicol Lett 78 253-262. 

Serum hormone concentrations reflect both the rate of secretion and clearance by peripheral tissues. In parallel with our studies on prolactin secretion we have evaluated the effects of dietary fat on the metabolic clearance rate of prolactin. Rats were initially treated with ergocryptine to suppress endogenous prolactin secretion. We then measured the disappearance of immuno-reactive prolactin from the sera after a single intravenous injection of prolactin. No significant effect of dietary fat on the clearance of prolactin was observed (Figure 4). 

On the other hand, the impact of ethylene in the composition of headspace gases fed to Taxus sp. cultures was very evident. The positive involvement of ethylene was also noted when cultures were elicited with both dissolved and volatilized methyl jasmonate and with chitin- and chitosan-derived oligosaccharides. The effect of the latter compounds on biosynthesis of ethylene by the plant cell cultures brings us to a better understanding of the interdependence of elicitor and hormone concentrations and of cross-talk signal transduction in plants. 

Fig. 1. Hormone secretion and control of the hypothalamic-pituitary-gonadal axis. Plus and minus signs indicate stimulation and inhibition respectively. In both male and female animals the dominant feedback effect of gonadal steroids on the hypothalamic-pituitary axis is inhibitory. The only major exception is in the female in which a rapid FSH-induced increase in the concentration of oestradiol triggers a large increase of the secretion of LH to induce ovulation. Note that LHRH secreted by the hypothalamus is carried directly to the pituitary gland without entering the peripheral circulation. Since the pituitary and gonadal hormones are secreted into the peripheral blood stream the functional response to hormone agonists or antagonists may be assessed by simple measurements of circulating hormone concentration ).

Emerson CH, Utiger RD (1975) Plasma thyrotropin-releasing hormone concentrations in the rat. Effect of thyroid excess and deficiency and cold exposure. J Clin Invest 56(6) 1564-70... 

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