Female reproductive cycle hormone

Male and female sex hormones. Influence secondary sexual characteristics regulate female reproductive cycle. 

The most frequent and prevalent use of the female hormones is in contraceptive preparations (see Hormonal Contraceptives ). The other primary indications for estrogen and progesterone are replacement of endogenous hormone production and subsequent resolution of symptoms related to hormonal deficiencies. This replacement can be especially important following menopause—that is, when the female reproductive cycle ceases and the associated cyclic production of the ovarian hormones ends. Specific clinical conditions that may be resolved by estrogen and progesterone are listed below. 

Hypogonadism. Estrogens, or a combination of estrogen and progesterone, may be used to treat abnormally low ovarian function. Appropriate use of these hormones induces the uterine changes and cyclic bleeding associated with the normal female reproductive cycle. 

Figure 33.3. The female reproductive cycle. FSH, follicle stimulating hormone GnRH, gonadotropin-releasing hormone LH, luteinizing hormone. (Reproduced with permission from Thomas, M. J., and Thomas, J. A. Toxic responses of the reproductive system. In Klaassen, C. D. (Ed.). Casarett and Doull s Toxicology, 6th ed. McGraw-Hill, New York, 2001, pp. 673-709.

Q2 Explain the profile of gonadotropic hormones activity, i.e. luteinizing hormone (LH) and follicle-stimulating hormone (FSH), in a typical 28-day female reproductive cycle... 

The utility of a set of long-term-acting regulators is evident the estrogens and progesterone that regulate the female reproductive cycle. In humans these hormones interact over a 4-week cycle to prepare the uterus for implantation of a fertilized ovum. 

Schematic of the female reproductive cycle and the influences of exogenously administered hormones.

The human female reproductive (ovarian) cycle is initiated and regulated by gonadotrophic hormones. Day 1 of the cycle is characterized by commencement of menstruation the discharge of fragments of the endometrium (wall of the womb) from the body, signifying fertilization has not occurred in the last cycle. At this stage, plasma levels of FSH and LH are low, but these begin to increase slowly over the subsequent 10-14 days. 

Progesterone ranks with estradiol as one of the key hormones that controls the reproductive cycle in the mammalian female. Progesterone, synthesized by a structure on the ovary that forms immediately after ovulation known as the corpus luteum, inhibits subsequent ovulation until the next cycle. Increased levels of progesterone are essential in... 

Hormonal patterns and their regulation are more complex in females than in males due to the female cycle, the fertilization process, gestation and lactation. All functions ofthe female reproductive system are under endocrine control and therefore can be disrupted by effects on the reproductive endocrine system. 

In summary, the menstrual cycle is primarily regulated by the interaction between pituitary and ovarian hormones. Also, releasing hormones from the hypothalamus plays a role in controlling female reproduction through their effects on LH and FSH release from the anterior pituitary.7 A complex series of positive and negative feedback mechanisms control the cyclic release of various female hormones.22,81,97 For instance, increased estrogen secretion in the follicular... 

Reproductive behavior in fish is a phenomenon that is synchronized by chemical means.138-140 A fraction of the steroids that are involved in the internal development of oocytes are released by females into the environment, where they are encountered by males — detection of this steroid induces internal hormonal changes in males that bring about enhanced sperm production. At a later time in the reproductive cycle, prostaglandins in the female that are associated with the follicular rupture of mature egg cells are released. Upon detection of the appropriate prostaglandin, males begin mating behaviors that culminate in the release of gametes by both sexes. 

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