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Biology LibreTexts

12: Endocrine System

  • Page ID
    16794
  • This chapter describes the endocrine system and its vital roles in communication, control, and homeostasis within the human body. The focus is on the pituitary gland, as the master gland of the endocrine system, and three other endocrine glands: the thyroid gland, adrenal glands, and pancreas. The chapter also explains the differing mechanisms of steroid and non-steroid endocrine hormones.

    • 12.1: Case Study: Hormones and Health
      18 year-old Gabrielle checks her calendar. It has been 42 days since her last menstrual period, two weeks later than the length of the average woman's menstrual cycle. Although many women would suspect pregnancy if their period was late, Gabrielle has not been sexually active.
    • 12.2: Introduction to the Endocrine System
      The patient in this photo has the characteristic moon face of a disorder named Cushing's syndrome.
    • 12.3: Endocrine Hormones
      The medication pictured above with the brand name Progynon was a drug used to control the effects of menopause in women.
    • 12.4: Pituitary Gland
      This adorable nursing infant is part of a positive feedback loop. When he suckles on the nipple, it sends nerve impulses to his mother’s hypothalamus, which "tell" her pituitary gland to release the hormone prolactin into her bloodstream.
    • 12.5: Thyroid Gland
      The woman in this photo has a goiter. A goiter is an abnormal enlargement of the thyroid gland, which is located in the neck. The formation of a goiter may occur in a number of different thyroid disorders. You'll learn why in this concept.
    • 12.6: Adrenal Glands
      The adrenal glands are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys. The right adrenal gland is smaller and has a pyramidal shape. The left adrenal gland is larger and has a half-moon shape.
    • 12.7: Pancreas
      Giving yourself an injection can be difficult, but for someone with diabetes, it may be a matter of life or death. The person in the photo has diabetes and is injecting himself with insulin, the hormone that helps control the level of glucose in the blood. Insulin is produced by the pancreas.
    • 12.8: Case Study Hormonal Conclusion and Chapter Summary
      Gabrielle, who you read about in the beginning of this chapter, has polycystic ovary syndrome (PCOS). PCOS is named for the multiple fluid-filled sacs, or cysts, that are present in the ovaries of women with this syndrome. You can see these cysts in the illustration above, which compares a normal ovary with a polycystic ovary. The cysts result from follicles in the ovary that did not properly produce and release an egg. Mature eggs are normally released from follicles monthly during the process

    Thumbnail: Thyroid and parathyroid glands. Image used with permission (Public Domain; NIH).