Other cells called osmoreceptors which Other cells, called osmoreceptors, which are also located in the hypothalamus, measure osmotic concentrations of body fluids and influence the secretion of AVP . Thryoid Gland • Thyroid Gland: The thyroid gland is an “H” shaped organ located in the neck. The thyroid gland secretes tri-iodothyronine/T3, thyroxin/T4 (from the follicular cells) and calcitonin (from the parafollicular cells). • Hormone Function • Tri-iodothronine/T3 - contains three iodide ions Increases the basal metabolic rate • Thyroxin/T4 - contains four ions of iodide Increases the basal metabolic rate
1/11/2010 15 Histology of the Thyroid Gland Thyroid Gland
1/11/2010 16 Goiter • Goiter: The term goiter refers to an enlargement of the thyroid gland. It is a nonspecific term that does not indicate a cause for the increase in size of the thyroid gland. Goiters are generally associated with hyperthyroidism (over-active thyroid gland) • Causes (most common) • Graves Disease Pregnancy: Human Chorionic Gonadotropin (HCG) induced • Hashimoto’s Thyroiditis Thyroid Cancer • Dietary Iodine Deficiency • Symptoms (general) • Tachycardia/Atrial fibrillation • Weight Loss • Eye Signs/Exopthalmos • Warm, Fine, Moist Skin • Sensitivity To Heat • Fatique • Insomnia • Increased Appetite/Bowel Habits Goiter
1/11/2010 17 Goiter Graves’ Disease • Graves’ Disease: Grave’s Disease is an autoimmune disorder also known as toxic diffuse goiter (thyrotoxicosis). The disorder is characterized by: • Hyperthyroidism • Goiter • Pretibial Myxedema: rare complication Pretibial Myxedema: rare complication characterized by a localized, non-pitting edema of the skin over the anterior aspect of the leg • Exopththalmus
1/11/2010 18 Exopthalmus • Exopthalmos is a term that describes a f d t i f th b ll forward protrusion of the eyeball characterized by a retracted upper eyelid and a rim of sclera between the upper lid and the superior portion of the iris. Exopthalmus
1/11/2010 19 Hashimoto’s Thyroiditis • Hashimoto’s Thyroiditis: Hashimoto’s thyroiditis is believed to be the most common cause of primary hyperthyroidism and is more common in females than males (8:1 incidence). It is autoimmune in nature and generally affects individuals between the ages of 30 and 50 years of age. Antibodies which resemble thyroid stimulating hormone (TSH) bind to the TSH receptors and provide a constant stimulation of thyroid function. Eventually the patient develops hypothyroidism after the thyroid gland is “burned out”. These patients will then be managed with thyroid hormone replacement therapy. Goitrogens • Goitrogens are substances found in foods that suppress thyroid gland function by that suppress thyroid gland function by interfering with the uptake of iodine. The reduced iodine uptake by the thyroid gland results in an enlargement of the thyroid gland (goiter). Foods in the Brassicae (cabbage) are known goitrogens Other (cabbage) are known goitrogens. Other goitrogenic foods include soy beans, peanuts, strawberries, peaches, pine nuts, radishes, and horseradish.
1/11/2010 20 Hypothyroidism: Myxedema Hypothyroidism