follicle-stimulating hormone

Examples of follicle-stimulating hormone in the following topics:

• Hormonal Regulation of the Male Reproductive System

  • The male reproductive system is regulated by the production, stimulation, and feedback of specific hormones.
  • If the pituitary gland is removed, spermatogenesis can still be initiated by follicle-stimulating hormone (FSH) and testosterone.
  • There it stimulates the synthesis and secretion of the gonadotropins, FSH and luteinizing hormone (LH).
  • Follicle-stimulating hormone (FSH)  is released by the anterior pituitary gland.
  • Follicle-stimulating hormone stimulates both the production of androgen-binding protein by Sertoli cells and the formation of the blood-testis barrier.

• Onset, Duration, and Half-Life of Hormone Activity

  • A hormone's half-life and duration of activity are limited and vary from hormone to hormone.
  • For instance, the biological half-life of luteinizing hormone is 20 minutes, which is shorter than that of a follicle-stimulating hormone (three to four hours), and of human chorionic gonadotropin (24 hours).
  • The duration of hormone activity refers to the duration of events that were stimulated by hormone-receptor binding.
  • Follicle-stimulating hormone 2.
  • Luteinizing hormone 4.

• Chemistry of Hormones

  • There are three classes of hormones: peptide hormones, lipid hormones, and monoamine hormones.
  • Some peptide hormones contain carbohydrate side chains  and are termed glyco-proteins, such as the follicle-stimulating hormone.
  • All peptide hormones are hydrophilic and are therefore unable to cross the plasma membrane alone.
  • Eicosanoids are also lipid hormones that are derived from fatty acids in the plasma membrane.
  • Unlike other hormones, eicosanoids are not stored in the cell—they are synthesized as required.

• Oogenesis

  • The menstrual cycle begins with the maturation of oocytes through the process of oogenesis, as well as concurrent follicle development that stimulates ovulation.
  • At the start of the menstrual cycle, some 12-20 primary follicles begin to develop under the influence of elevated levels of follicle-stimulating hormone (FSH) to form secondary follicles.
  • On day 14 of the cycle, a luteinizing hormone surge is triggered by the positive feedback of estrogen.
  • This causes the secondary follicle to develop into a tertiary follicle, which then leaves the ovary 24–36 hours later.
  • Differentiate among the stages of oogenesis and the actions of hormones during each stage

• Hormonal Regulation of the Female Reproductive Cycle

  • Follicle-stimulating hormone (FSH) is secreted by the anterior pituitary gland beginning in the last few days of the previous menstrual cycle.
  • The rise in FSH recruits tertiary-stage ovarian follicles (antral follicles) for entry into the menstrual cycle.
  • Follicle-stimulating hormone induces the proliferation of granulosa cells in the developing follicles and the expression of luteinizing hormone (LH) receptors on these cells.
  • This increased level of estrogen stimulates production of gonadotropin-releasing hormone (GnRH), which increases production of LH.
  • In the preovulatory phase of the menstrual cycle, the ovarian follicle undergoes cumulus expansion stimulated by FSH.

• Hormone Receptors

  • A hormone receptor is a molecule that binds to a specific hormone.
  • Receptors for peptide hormones tend to be found on the plasma membrane of cells, whereas receptors for lipid-soluble hormones are usually found within the cytoplasm.
  • The hormone activity within a target cell is dependent on the effective concentration of hormone-receptor complexes that are formed.
  • Many hormones are composed of polypeptides—such as thyroid-stimulating hormones, follicle-stimulating hormones, luteinizing hormones, and insulin.
  • Lipophilic hormones—such as steroid or thyroid hormones—are able to pass through the cell and nuclear membrane; therefore receptors for these hormones do not need to be, although they sometimes are, located in the cell membrane.

• The Anterior Pituitary

  • Thyroid-stimulating hormone is a glycoprotein hormone that affects the thyroid gland and the secretion of thyroid hormones.
  • Follicle-stimulating hormone is a glycoprotein hormone that targets the gonads and effects the growth of the reproductive system.
  • Luteinizing hormone is a glycoprotein hormone that targets the gonads to effect sex-hormone production.
  • Growth hormone is a polypeptide hormone that targets the liver and adipose tissue and promotes growth through lipid and carbohydrate metabolism.
  • Hormone secretion from the anterior pituitary gland is regulated by hormones secreted by the hypothalamus.

• Interactions of Hormones at Target Cells

  • Insulin stimulates the liver and most other body cells to absorb glucose.
  • Glucagon stimulates the liver to release glucose.
  • Glucagon also stimulates the production of ketone bodies from amino acids and fatty acids.
  • For example, testosterone and follicle- stimulating hormones are required for normal sperm production.
  • Glucagon is a pancreatic peptide hormone that, as a counter-regulatory hormone for insulin, stimulates glucose release by the liver and maintains glucose homeostasis.

• Ovarian Cycle

  • The main hormone controlling this stage is estradiol.
  • During the follicular phase, follicle-stimulating hormone (FSH) is secreted by the anterior pituitary gland.
  • FSH induces the proliferation of granulosa cells in the developing follicles and the expression of luteinizing hormone (LH) receptors on these granulosa cells.
  • Crypts in the cervix are also stimulated to produce fertile cervical mucus that reduces the acidity of the vagina, creating a more hospitable environment for sperm.
  • After ovulation, the pituitary hormones FSH and LH cause the remaining parts of the dominant follicle to transform into the corpus luteum.

• Formation, Storage, and Release of Thyroid Hormones

  • Thyroid hormones (T4 and T3) are produced by the follicular cells of the thyroid gland and regulated by thyroid-stimulating hormone (TSH).
  • The thyroid hormones thyroxine (T4) and triiodothyronine (T3) are produced from thyroid follicular cells within the thyroid gland, a process regulated by the thyroid-stimulating hormone secreted by the anterior pituitary gland.
  • In this process, sodium is co-transported with iodide from the basolateral side of the membrane into the cell, and then concentrated in the thyroid follicles to about thirty times its concentration in the blood.
  • T4 is believed to be a pro-hormone and a reservoir for the more active and main thyroid hormone T3.
  • A lack of thyroid hormone will lead to decreased negative feedback on the pituitary, which in turn, will lead to increased production of thyroid-stimulating hormone, which causes the thyroid to enlarge (goiter).