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.

• Lipid-Derived, Amino Acid-Derived, and Peptide Hormones

  • All hormones in the human body can be divided into lipid-derived, amino acid-derived, and peptide hormones.
  • The primary class of lipid hormones in humans is the steroid hormones.
  • Examples of steroid hormones include estradiol, which is an estrogen, or female sex hormone, and testosterone, which is an androgen, or male sex hormone.
  • This class also includes small proteins, such as growth hormones produced by the pituitary, and large glycoproteins, such as follicle-stimulating hormone produced by the pituitary .
  • The structures of peptide hormones (a) oxytocin, (b) growth hormone, and (c) follicle-stimulating hormone are shown.

• 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.

• Female Hormones

  • As with the male, the hypothalamic hormone GnRH (gonadotropin-releasing hormone) causes the release of the hormones FSH (follicle stimulating hormone) and LH (luteinizing hormone) from the anterior pituitary.
  • In females, FSH stimulates the development of egg cells, called ova, which develop in structures called follicles.
  • Follicle cells produce the hormone inhibin, which inhibits FSH production.
  • LH also plays a role in the development of ova, as well as in the induction of ovulation and stimulation of estradiol and progesterone production by the ovaries.
  • There are still eggs and potential follicles on the ovaries, but without the stimulation of FSH and LH, they will not produce a viable egg to be released.

• Hormonal Regulation of the Reproductive System

  • During puberty, in both males and females, the hypothalamus produces gonadotropin-releasing hormone (GnRH), which stimulates the production and release of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary gland.
  • It is also called interstitial-cell-stimulating hormone.
  • In females, FSH stimulates development of egg cells (or ova) in structures called follicles.
  • Follicle cells produce the hormone inhibin, which inhibits FSH production in the female reproductive system.
  • GnRH secreted by the hypothalamus stimulates the release of FSH, which stimulates the growth of egg cells, and LH, which signals for the the ovulation of an egg from its follicle.

• Thyroid Gland

  • The thyroid gland is made up of many spherical thyroid follicles which are lined with a simple cuboidal epithelium.
  • These follicles contain a viscous fluid, called colloid, which stores the glycoprotein thyroglobulin.
  • The follicles produce hormones that can be stored in the colloid or released into the surrounding capillary network for transport to the rest of the body via the circulatory system.
  • Follicle cells are stimulated to release stored T3 and T4 by thyroid-stimulating hormone (TSH), which is produced by the anterior pituitary.
  • It acts in the bones to inhibit osteoclast activity and in the kidneys to stimulate excretion of calcium.

• 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).