Sex steroids .pdf

14/11/23 Sex steroids: testosterone, oestrogen and progesterone Learning objective: de ned the main key sex steroids: testosterone, oestrogen and progesterone. Learning objective: expend the role of aromatase brie y. Learning objective: describe the feedback loop bet ween sex steroids and LH/FSH. Le...

14/11/23 Sex steroids: testosterone, oestrogen and progesterone Learning objective: de ned the main key sex steroids: testosterone, oestrogen and progesterone. Learning objective: expend the role of aromatase brie y. Learning objective: describe the feedback loop bet ween sex steroids and LH/FSH. Learning objective: de ne hypogonadism as a clinical example. Key roles of sex hormones: Promote sexual differentiation. Development of secondary sexual characteristics. Regulate sexual behaviour. Supporting normal reproductive function. Support bone growth and maintain bone mass. Core structure: Cyclopentanoperhydrophenanthrene ring also called the steroid nucleus or sterane. Most reactions occur at carbon 17 on the side chain. Action of steroid hormones ( genomic ): Most of the steroids have receptors within the nucleus, and the action that occurs because of this interaction is called a genomic action. There is also non-genomic action. Non-genomic actions can happen in a quicker manner. An example would be oestrogen, oestrogen can act directly on G protein coupled receptors and signal the production of different kinases producing different physiological effects within the cell. Testosterone: It is produced by Leydig cells in testicles and the theca interna cells of ovaries. Testosterone secretion is under the control of LH, a pituitary glycoprotein hormone. Testosterone secretion has pulsatile, diurnal and circadian rhythms, highest concentrations when waking up and low concentrations in the afternoon/evenings. Functions: During embryonic development, it regulates the differentiation of the Wolf an ducts into epididymis, vas deferens. It promotes somatic growth and virilisation in boys. It is essential for maintaining sexual function, and germ cell development. It regulates secondary sexual/non-sexual characteristics and muscle growth. Testosterone regulation: The Sertoli cells nurse the spermatogonium to develop bet ween the Sertoli cells until they become adult sperms in the lumen. produce I Testosterone Estrogens: 3 Estrogens- esterone, estradiol and estriol. The main type is estradiol. Predominant production in ovaries by granulosa cells, also produced locally in tissues. Estradiol also produced from conversion of circulating androgens by aromatisation. Secretion is under the in uence of LH and FSH, which are gonadotropin hormones secreted by anterior pituitary gland. Functions: It regulate secondary sexual female characteristics and sexual behaviour. It is responsible for secretary activity within the genital tract. It regulates GnRH secretion, and for ovulation during a menstrual cycle. Regulates cardiovascular physiology and neuronal growth, bone structure and integrity. collective term used jgg.ES F Progesterone: Progesterone is the main progestin secreted by the corpus luteum. It embeds a fertilised ovum and maintains pregnancy. It induces decidualisation of the endometrium, inhibits uterine contractions, increases viscosity of cer vical mucus, promotes breast development, increases body temperature and it inhibits GnRH release. Summary for revision: Menstrual cycle: Cycle there is bet ween 28 to 35 days. First day of menses is the rst day of the cycle; menses last about four days. Follicular or proliferative phase begins with onset of menses, last 14 to 21 days. FSH plays an important role during this phase – follicular recruitment, growth, increased oestrogen secretion, by the follicle; appearance of LH receptors on granulosa cells in preparation for LH surge. LH pulse frequency every 90 minutes. Ovulation is triggered by rapid rise in oestradiol level. Positive feedback of oestradiol level at pituitary and hypothalamus result in LH surge. LH surge essential for release of ovum and formation of corpus luteum, usually happens 36 hours after the surge. Aromatase: Aromatase is an important enzyme in the steroidogenesis pathway. It is present in several tissues. It is responsible for the conversion of androstenedione to estrone and testosterone to estradiol in peripheral tissues. Aromatase de ciency, result in overproduction of testosterone; females affected by this are born with ambiguous genitalia.