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Matthew J. Van Sant
Associate Professor
Department of Agriculture, Biology and Health Sciences
Cameron University
Barbara‚Äôs Thyroid: How Negative Feedback Can Be Positive

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.