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Barbara’s Thyroid

How Negative Feedback Can Be Positive


Author(s)

Matthew J. Van Sant
Department of Agriculture, Biology and Health Sciences
Cameron University
mvansant@cameron.edu

Abstract

This directed case study on thyroid dysfunction was written to help students understand how negative feedback pathways work. The title character suffers from hypothyroidism, and although a specific cause cannot be determined from the information provided without further testing, she likely has secondary (pituitary disorder) or tertiary (hypothalamic disorder) hypothyroidism. Students evaluate results from a blood test and answer a series of guided questions to ultimately develop a diagnosis. Although the case study focuses on the thyroid gland, it should also help students understand any pathway involving the hypothalamic-pituitary axis since the negative feedback pathway is very similar for other endocrine organs controlled by the same axis. Students conclude the case by applying what they have learned to the hypothalamic-pituitary-gonadal axis. Originally developed for a sophomore-level human physiology course consisting of pre-nursing, biology and chemistry majors, the case would best be used after covering the hormones produced by the hypothalamus, anterior pituitary and associated target organs.


Objectives

  • Describe the general principles of negative feedback pathways.
  • Explain how the hypothalamus controls the anterior pituitary through hormone secretion.
  • Explain how the anterior pituitary controls the thyroid through hormone secretion.
  • Illustrate how thyroid hormones provide negative feedback to the hypothalamus and anterior pituitary.
  • Determine how elevated or decreased levels of a hormone produced by any of these three organs will affect the secretions of the other hormones in the pathway.
  • Summarize the role of trophic hormones; specifically, explain why their presence or absence causes other organs to grow or atrophy.
  • Apply these skills to other endocrine glands in the hypothalamic-anterior pituitary axis to predict how other trophic hormones affect their target organs.

Keywords

Endocrine; thyroid; T3; T4; TSH; hypothyroidism; hypothalamus; anterior pituitary; negative feedback

Topical Areas

N/A

Educational Level

Undergraduate lower division, Undergraduate upper division

Format

PDF

Type / Methods

Directed

Language

English

Subject Headings

Physiology  |   Medicine (General)  |   Nursing  |  


Date Posted

11/1/2018

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