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Feedback Loop Project

Grave's Disease Ananda Zhu and Vian Le
by

Ananda Zhu

on 28 May 2011

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Transcript of Feedback Loop Project

Grave'sDisease What is Grave's Disease? A thyroid-specific autoimmune disorder that makes antibodies to the TSHr (thyroid-stimulating hormone receptor) on the thyroid cells, thus leading to hyperthyroidism. Hyperthyroidism: an abnormally strong release of hormones (T4, T3) from the thyroid gland. Regular Thyroid Negative Feedback Loop pituitary thyroid-stimulating hormone
(TSH) TSH causes the thyroid gland to release thyroid hormones - T4 (thyroxine) and T3 (triidothyronine). How is the feedback loop affected by Grave's disease? thyroid cell TSH receptors autoantibodies thyroid hormones (T4 and T3) Grave's disease is an immune disorder in which the immune system mistakenly attacks the thyroid gland as a foreign invader.
As a result, antibodies are produced. The autoantibodies bind to TSH receptors on thyroid cells. The binding of antibodies to TSH receptors stimulate the thyroid cell to secrete thyroid hormones. Why is this not a negative feedback loop? Autoantibodies are not subject to the negative feedback loop. The negative feedback loop only affects the level of TSH, not the level of antibodies. The production of antibodies is controlled by the immune system. As a result, the antibodies will continuously bind to the receptors, leading to a steady increase in the level of thyroid hormones. What does hyperthyroidism cause? exophthalmos eyes that are enlarged and protrude pretibial myxedema swollen shins diffuse goiter enlargement of the thyroid gland The concentration of thyroid hormones and cell metabolic rate decreased beyond normal levels. Homeostasis is disturbed. Hypothalamus releases TRH. hypothalamus negative feedback negative feedback As the level of thyroxine rises beyond normals levels,
the feedback loop is stopped. thyroid gland thyroid hormones (T4 and T3) thyroid-releasing hormone
(TRH) TRH causes the anterior pituitary to release TSH. The levels of thyroid hormones and the cell metabolic rate are increased back to normal levels. Homeostasis is restored. HOMEOSTASIS Several symptoms are observed in patients with Grave's disease (hyperthyroidism) as a result of the over-stimulation of the thyroid gland and extra secretion of thyroid hormones. TSH inhibits the release of TRH in the hypothalamus. With no TRH being produced, the pituitary no longer secretes TSH. The loop is stopped.
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