Created by CK-12 Foundation/Adapted by Christine Miller
Case Study: Hormonal Havoc
Eighteen-year-old Gabrielle checks her calendar. It has been 42 days since her last menstrual period, which is two weeks longer 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. She is not even sure she is “late,” because her period has never been regular. Ever since her first period when she was 13 years old, her cycle lengths have varied greatly, and there are months where she does not get a period at all. Her mother told her that a girl’s period is often irregular when it first starts, but five years later, Gabrielle’s still has not become regular. She decides to go to the student health center on her college campus to get it checked out.
The doctor asks her about the timing of her menstrual periods and performs a pelvic exam. She also notices that Gabrielle is overweight, has acne, and excess facial hair. As she explains to Gabrielle, while these physical characteristics can be perfectly normal, in combination with an irregular period, they can be signs of a disorder of the endocrine — or hormonal — system called polycystic ovary syndrome (PCOS).
In order to check for PCOS, the doctor refers Gabrielle for a pelvic ultrasound and sends her to the lab to get blood work done. When her lab results come back, Gabrielle learns that her levels of androgens (a group of hormones) are high, and so is her blood glucose (sugar). The ultrasound showed that she has multiple fluid-filled sacs (known as cysts) in her ovaries. Based on Gabrielle’s symptoms and test results, the doctor tells her that she does indeed have PCOS.
PCOS is common in young women. It is estimated that 6-10% women of childbearing age have PCOS — as many as 1.4 million women in in Canada. You may know someone with PCOS, or you may have it yourself.
Read the rest of this chapter to learn about the glands and hormones of the endocrine system, their functions, how they are regulated, and the disorders — such as PCOS — that can arise when hormones are not regulated properly. At the end of the chapter, you will learn more about PCOS, its possible long-term consequences (including fertility problems and diabetes), and how these negative outcomes can sometimes be prevented with lifestyle changes and medications.
In this chapter, you will learn about the endocrine system, a system of glands that secrete hormones that regulate many of the body’s functions. Specifically, you will learn about:
- The that make up the , and how s act as chemical messengers in the body.
- The general types of endocrine system disorders.
- The types of endocrine hormones — including steroid hormones (such as sex hormones) and non-steroid hormones (such as insulin) — and how they affect the functions of their target cells by binding to different types of receptor proteins.
- How the levels of hormones are regulated mostly through negative, but sometimes through positive, feedback loops.
- The master gland of the endocrine system, the , which controls other parts of the endocrine system through the hormones that it secretes, as well as how the pituitary itself is regulated by hormones secreted from the of the brain.
- The and its hormones — which regulate processes including metabolism and calcium — how the thyroid is regulated, and the disorders that can occur when there are problems in thyroid hormone regulation (such as hyperthyroidism and hypothyroidism).
- The , which secrete hormones that regulate processes such as metabolism, electrolyte balance, responses to stress, and reproductive functions, and the disorders that can occur when there are problems in adrenal hormone regulation, such as Cushing’s syndrome and Addison’s disease.
- The , which secretes hormones that regulate blood glucose levels (such as insulin), and disorders of the pancreas and its hormones, including .
Later chapters in this book will discuss the glands and hormones involved in the reproductive and immune systems in more depth.
As you read this chapter, think about the following questions:
- Why can hormones have such broad range effects on the body, as we see in PCOS?
- Which hormones normally regulate blood glucose? How is this related to diabetes?
- What are androgens? How do you think their functions relate to some of the symptoms that Gabrielle is experiencing?
Mayo Clinic Staff. (n.d.). Polycystic ovary syndrome [online article]. MayoClinic.com. https://www.mayoclinic.org/diseases-conditions/pcos/multimedia/polycystic-ovary-syndrome/img-20007768
A group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).
The body system which acts as a chemical messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In humans, the major endocrine glands are the thyroid gland and the adrenal glands.
A hormone is a signaling molecule produced by glands in multicellular organisms that target distant organs to regulate physiology and behavior.
The master gland of the endocrine system that secretes many hormones, the majority of which regulate other endocrine glands.
A part of the brain that secretes hormones and connects the brain with the endocrine system.
A large endocrine gland in the neck whose hormones control the rate of cellular metabolism and help maintain calcium homeostasis.
The ability of an organism to maintain constant internal conditions despite external changes.
one of a pair of glands located on top of the kidneys that secretes hormones such as cortisol and adrenaline
A long, flat gland that sits tucked behind the stomach in the upper abdomen. The pancreas produces enzymes that help digestion and hormones that help regulate the way your body processes sugar (glucose).
A disease caused by problems with the pancreatic hormone insulin, which leads to high blood glucose levels and symptoms such as excessive thirst and urination; includes type 1 and type 2 diabetes.