My Brother Calls Me Bug Eyes

Case Study #1: My Brother Calls Me ‘Bug Eyes’”

1. Thyroxine(T4) - a major hormone secreted by the thyroid follicles; constructed from two linked tyrosine amino acids and has four bound iodine atoms

Triiodothyronine(T3) - formed at the target tissues by conversion of T4 to T3; also constructed from two linked amino acid and has three bound iodine atoms (Marieb & Hoehn, 2013).

2. One effect of the thyroid hormone is a calorigenic effect, which increases body heat production and metabolic rate. With an overactive thyroid, this would mean her heart rate and heat production would further increase beyond the normal range (Marieb & Hoehn, 2013).

3. Thyroid stimulating hormone (TSH) follows a hypothalamic-pituitary-target endocrine organ feedback loop, and the thyrotropin-releasing hormone (TRH) triggers the release of TSH from the thyrotropic cells of the anterior pituitary gland (Marieb & Hoehn, 2013).

4. Under normal conditions, the secretion of TSH is regulated a rising blood levels of thyroid hormones act on both the pituitary and hypothalamus to inhibit TSH secretion. Growth hormone-inhabiting hormone (GHIH) also inhibits TSH secretion (Marieb & Hoehn, 2013).

5. When antibodies stimulate TSH receptors on the thyroid gland, this causes the thyroid to continuously release the thyroid hormone (TH) and become overactive. This is where we see symptoms of elevated metabolic rate, sweating, nervousness, weight loss, etc. (Marieb & Hoehn, 2013).

6. When TH levels are high, which they are in Krista's case because of the overactive thyroid, the pituitary responds by inhibiting the hypothalamic-anterior pituitary axis and temporarily suits off the stimulus for TSH release. This results in a lower level of TSH, even though the TH level increases (Marieb & Hoehn, 2013).

7. In contrast to the above example of a negative feedback loop, if Krista had been diagnosed with hypothyroidism and her TH levels were low, this would actually increase her levels of TSH (Marieb &...