Testes, hormones produced

A separate protein hormone produced primarily in the testis, called inhibin, also affects the secretion of FSH. Inhibin has been isolated primarily from testicular extracts but also may be found in the antral fluid of ovarian follicles in females. Inhibin decreases the release of FSH from the pituitary but does not affect hypothalamic production of GnRH. 

Endocrine disruption which is independent of interactions between xenobiotics and endogenous hormone receptors can occur in a variety of different ways, including alterations in the number of hormone receptor sites (up- or down-regulation) or direct or indirect hormone modifications which alter hormonal function (Evans, 2007 Keith, 1997). Xenobiotics can change the rate of synthesis or destruction of endogenous hormones and can alter how hormones are stored, how they are released into and/or transported within the circulation, or even how they are eventually cleared from the body (Capen, 2008 Evans, 2007 Keith, 1997 Sikka et al, 2005). Any xenobiotic toxic to hormone-producing organs or tissues (e.g. testis and ovary) also has the potential to decrease hormone synthesis and thereby indirectly cause endocrine disruption (Devine and Hoyer, 2005 Evans, 2007). 

An androgenic steroid the male sex hormone produced by the testis. It has six times the androgenic activity of its metabolic product, androsterone. Properties White or slightly cream-white crystals or crystalline powder odorless stable in air. Mp 153-157C. Dextrorotatory in dioxane solution very soluble in chloroform soluble in alcohol, dioxane, and vegetable oils slightly soluble in ether insoluble in water. 

In Table I are fisted the various names for the most widely available androgenic-anabolic agents. Testosterone itself was synthesized before it was known to be the major hormone produced by the testis. The myriads of synthetic routes to this material have been reviewed frequently, and the agent itself and its esters are so abundantly available at reasonable prices that the synthesis will not be considered here. 

These cells arise from interstitial mesenchymal tissue between the tubules during the eighth week of human embryonic development. They are located in the connective tissue between the seminiferous tubules, Leydig cells are the endocrine cells in testis that produce testosterone from cholesterol via a serie.s of enzymatic pathways and steroidal intermediates under the control of luctinizing hormone (LH) from pituitary. The effects of testosterone can be grouped into the following categories ... 

Female sexual development and behaviour in mammals occurs by default and requires no ovarian secretion, and it is only in genetic males that the testis can secrete hormones which destroy this female pattern and superimpose that of the male. Sexual differentiation is not so well defined in fish, and larval exposure to both synthetic estrogens and androgens is widely used in aquaculture to produce monosex cultures. Endocrine disruption of sexual differentiation in fish may therefore reflect both the complexity and diversity of such processes between different species. Some care is required in use of the terms hermaphrodite and sex-reversal since a true hermaphrodite has both functional testes and ovaries and a sex-reversed fish is fully functional as its final sex—both produce the appropriate viable gametes. Such functional sex-reversal is not possible in mammals, but in some species of fish it is the normal developmental pattern. In most of the cases of hermaphroditism or sex-reversal reported in the non-scientific press, there is evidence only for a few ovarian follicles within a functional testis. This may be considered as feminisation or a form of intersex, and is very clearly endocrine disruption, but it is certainly neither sex-reversal nor hermaphroditism. In some cases the terms have even been used to infer induction of a single female characteristic such as production of yolk-protein by males. 

The reproductive system includes the ovaries in the female and testes in the male, together with the ducts and tubes in which the ovum or spermatozoa travel and meet in the fallopian tube, and the environment in which the foetus develops. Since both ovary and testis produce hormones, there is overlap with the endocrine system (Chapters 12 and 19). 

In men, approximately 8 mg of testosterone is produced daily. About 95% is produced by the Leydig cells and only 5% by the adrenals. The testis also secretes small amounts of another potent androgen, dihydrotestosterone, as well as androstenedione and dehydroepiandrosterone, which are weak androgens. Pregnenolone and progesterone and their 17-hydroxylated derivatives are also released in small amounts. Plasma levels of testosterone in males are about 0.6 mcg/dL after puberty and appear to decline after age 50. Testosterone is also present in the plasma of women in concentrations of approximately 0.03 mcg/dL and is derived in approximately equal parts from the ovaries and adrenals and by the peripheral conversion of other hormones. 

The seeds of fenugreek produced an antifertility effect in female rabbits and a toxicity effect in male rabbits (Kassem et al., 2006). Feeding diets containing 30% fenugreek seeds resulted in a reduction of testis weight in males and damage to the seminiferous tubules and interstitial tissues. In addition, the plasma concentration of the antrogen hormone and sperm concentrations was halved in treated animals. In the case of females, development of the fetus was reduced. 

The hypothalamus produces gonadotropin releasing hormone (GnRH), which causes the anterior pituitary to release FSH and LH, which act on both the ovary and the testis. 

Testosterone (T), the male hormone par excellence, is primarily produced in the testis. It is metabolized to the more potent dihydrotestosterone (DHT). Physiological T concentrations reflect the balance between biosynthesis and metabolism. Therefore, T is a prime... 

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