Sexual hormones are of two types: The steroids have a molecular weight of about daltons, presenting thus a small size. Because of their size and lipo-solubility soluble in fatthey can easily diffuse through target cells, having consequently intra-cellular receptors. While the protein hormones weigh more than 5. The steroids can circulate in the blood stream, only if bound to non-specific proteins like albumin, or to specific proteins like SHBG sex hormone binding globulin.
On the other hand, the protein hormones are hydro-soluble and circulate freely in the blood. These hormones are produced by
Functions of the main sex hormones tissues pituitary and placenta and their main function is gonadic regulation ovaries and testicles.
FSH is a glycoprotein produced by the pituitary gland and has a molecular weight of about Morphologically, it is a heterodimer composed by two different sub-units: The a sub-unit 89 aminoacids is common to all gonadotropins and also to Functions of the main sex hormones thyrotrophic hormone. The b sub-unit aminoacids is specific for FSH. The main function of FSH is to promote and sustain the ovarian follicular growth in women and the spermatogenesis in men.
FSH stimulates also the synthesis of its own receptor on the granulosa and Sertoli cells and the LH receptor on granulosa cells. It stimulates the aromatase activity inside the granulosa cells the enzyme converting the androgens into oestrogens. Thus, FSH is responsible for " the choice of the dominant follicle". FSH synthesis and secretion by the hypophysis is controlled by different regulators, like: GnRH gonadotropin releasing hormone of hypothalamic originovarian oestrogens, activine and inhibine both of gonadic origin.
LH is a glycoprotein with a molecular weight of approximately The principal functions of LH are: LH synthesis and secretion from the hypophysis is controlled by different regulators, like GnRH gonadotropin releasing hormone of hypothalamic origin and ovarian oestrogens and progesterone. It is a heterodimer composed by two different sub-units: The specific b sub-unit contains aminoacids and can be distinguished from the b sub-unit of LH only by 30 aminoacids in the C terminal part of the molecule.
The free b sub-unit circulates also in the blood. A particular form of hCG, called "nicked" hCG, is a holo-hCG or a free b sub-unit, where the bond between the 46th and the 47th aminoacid is broken. This gives rise to a particular tri-dimensional form of the molecule, making it often difficult to be recognised by the antibodies used for its measurement.
The immunological recognition of "nicked" forms is specially important when hCG is measured to determine the "Functions of the main sex hormones" of a mother to carry a trisomy 21 baby known as the "What if, double test or triple test"as in this chromosomal pathology, the "nicked" forms increase significantly.
The function of hCG is essential to maintain the corpus luteum of pregnancy and its progesterone secretion. Human prolactin is a non-glycosylated protein, which contains a simple polypeptide chain of aminoacids.
It is structurally similar to hPL human placental lactogen and to growth hormone GH. In the circulation, prolactin can appear in its monomeric little prolactin or polymeric form big or big-big prolactinas well. The quantitative relationship between these different forms varies according to physiologic and pathologic conditions and according to the antibody used for their measurement. Prolactin is essentially of pituitary origin, but the stromal cells Functions of the main sex hormones the endometrium produce prolactin during the secretory phase, as well.
This hormone is considered as a marker of decidualisation. The principal biological function of prolactin in women is to control breast development and lactation.
The role of prolactin in men and of endometrial prolactin in women is not yet known. If progesterone is the main regulator of endometrial prolactin, the pituitary prolactin is essentially controlled by dopamine called also PIF or prolactin inhibiting factor.
However, TRH thyroid releasing hormone and VIP vasoactive intestinal peptide are capable of stimulating the release of pituitary prolactin. Oestrogens are of three types: At equal concentrations, E2 has a stronger biological effect than E1 which is more powerful than E3.
E2 can be reversibly converted to E1 and E1-sulphate. This sulphate is quantitatively the most important metabolite in the circulation. The enzymatic conversion of oestrogens occurs in the liver. Oestrogens are excreted in the urine as glucuronides or sulphates. In women of reproductive age, E2 is essentially produced by the enzymatic conversion of androgens androstenedione and testosterone. The androgens are produced by the thecal cells under the influence of LH and their conversion in E2 occurs Functions of the main sex hormones the granulosa cells of the follicle, through the enzyme aromatase.
Aromatase activity depends on FSH levels. Thus, a harmonious secretion of E2 is dependent on the two pituitary gonadotropins. In the post-menopausal women, the low level of Functions of the main sex hormones is provided by peripheral liver, fat and muscular tissues conversion aromatisation of androgens secreted by the adrenal glands.
The principal functions of E2 in women is the mitotic effect on "Functions of the main sex hormones" uterine mucosa and on the breast, the feed-back positive and negative on pituitary gonadotropins and its role in bone mineralisation. In women of reproductive age, E1 is mainly produced from the enzymatic conversion of androstenedione, which is secreted under the influence of LH by the thecal cells. The aromatase activity depends on FSH.
In the menopausal women and in men, E1 and its sulphate represent the main circulating oestrogens. The biological function of E1 is still speculative, but it could be related to the regulatory effect that the conversion of E1 into E2 has on the degree of oestrogenisation.
In women of reproductive age, the very low concentrations of E3 are produced by hepatic hydroxylation of E1 and E2. During pregnancy, E3 is produced in large quantities from the foeto-placental unit. As hydroxylase is lacking in the placenta and 3-b -hydroxy-dehydrogenase is absent in the foetus, the E3 production is dependent on a foeto-placental collaboration.
The mechanism is as follows, placental pregnenolone the precursor of progesterone is reduced to dehydroepiandrosterone sulphate DHEAS in the foetal adrenal glands. The E3 concentrations strongly increase during pregnancy, reflecting thus the foeto-placental co-operation.
For this reason the level of E3 has been used for a long time to assess high-risk pregnancies. The biological role of E3 remains still unknown.
In non-pregnant women of reproductive age, P4 is essentially of ovarian origin, the participation of the adrenal cortex is negligible. In the middle of the menstrual cycle, it is the LH peak which induces biochemical and phenotypical changes of granulosa cells, called also "the process of luteinisation". This process makes the granulosa cells capable to produce progesterone. Thus, progesterone, which becomes detectable from midcycle onwards, is essentially produced by the corpus luteum.
On the other hand, progesterone inhibits uterine contractions. Progesterone synthesis in the corpus luteum is stimulated by LH and hCG. The regulation of progesterone production in the placenta is not yet known, but it is thought to be partly dependent on hCG. In women of reproductive age, T is produced by the thecal cells which surround the follicle.
This androgen T serves as a substrate for the synthesis of E2, but it is also detected in circulation, even in very low concentrations.
In men testosterone is produced by Leydig cells, but the contribution of adrenal androgens cannot Functions of the main sex hormones neglected, especially in certain pathologies of the new born.
The biological role of T in women is to favour follicular atresia a follicle which has a diminished capacity of aromatisation cannot aromatise all androgens becomes atretic.
In men, T provides the appearance of secondary sex characteristics voice, pilosity and controls gonadotropins secretion. Edited by Aldo Campana.
The Role of Sex Hormones. Hormones are extremely important to our bodies, particularly the sex hormones. Everyone single person has some. Nihon Rinsho. Apr;73(4) [Sex hormones and physiological function ]. [Article in Japanese].
Yamatani H, Takahashi K, Nagase S. Sex hormones as. Sexual hormones are of two types: proteins and steroids. proteins like albumin, or to specific proteins like SHBG (sex hormone binding globulin). The main function of FSH is to promote and sustain the ovarian follicular growth in women.