Thyroid t4,t3,tsh

Thyroid t4,t3,tsh

1. THYROID T4,T3,TSH OMAR ALJABRI

2. introduction The thyroid hormones are tyrosine-based hormones produced by the thyroid gland that are primarily responsible for regulation of metabolism

3. THYROID GLAND

4. Biosynthesis Two biologically active thyroid hormones: 1)Tetraiodothyronine (T4 -thyroxine) 2)Triiodothyronine (T3) Derived from modification of tyrosine Thyroglobulin Pituitary produces Thyroid-Stimulating Hormone -TSH- which binds to follicle cell receptors. The follicle cells of the thyroid produce thyroglobulin.

5. REGULATION Thyroid hormones are lipid-soluble. found in the circulation associated with binding proteins: Thyroid Hormone-Binding Globulin(70%) Pre-albumin (transthyretin) (14%) Albumin (~15%) Less than 1% free Only free and albumin-bound thyroid hormone is biologically available to tissues .

6. Thyroid-Stimulating Hormone TSH TSH is produced by the anterior pituitary. TSH is a glycoprotein hormone composed of two subunits: alpha subunit: (common to LH, FSH) TSH beta subunit: which gives specificity of receptor binding and biological activity.

7. ROLE AND REGULATION OF TSH TSH acts on follicular cells of thyroid. Increases iodide transport into follicular cells Increases production of thyroglobulin Increases endocytosis of colloid from lumen into follicular cells Thyroid-Stimulating Hormone release is influenced by: hypothalamic TRH thyroid hormones themselves . Thyroid hormones exert negative feedback on TSH release at the level of the anterior pituitary. inhibition of TSH synthesis decrease in pituitary receptors for TRH

8. CONVERSION OF T4 TO T3 The thyroid secretes about 80mg of T4, but only 5mg of T3 per day. T3 has much greater biological activity than T4. A large amount of T4 (25%) is converted to T3 in peripheral tissues. In addition to T3, an equal amount of “Reverse T3 ” also formed . This conversion takes place mainly in the liver and kidneys.

9. Normal values Thyroid Test Reference Range TSH 0.5-4.70 µIU/mL Total T4 4.5-12.5 µg/ dL Free T4 0.8-1.8 ng/ dL Total T3 80 -200 ng/ dL Free T3 2.3- 4.2 pg /mL RT3 10-24 ng/ dL

10. Physiological and metabolic effect A-Metabolism: Thyroid hormones stimulate metabolic activities most tissues, leading to an increase in basal metabolic rate . increase body heat production, increased oxygen consumption and rates of ATP hydrolysis. Lipid metabolism : Increased thyroid hormone stimulate fat mobilization. Enhance oxidation of fatty acids in many tissues. Plasma concentrations of cholesterol are inversely correlated with thyroid hormone levels - one diagnostic indiction of hypothyroidism is increased blood cholesterol concentration . 2. Carbohydrate metabolism : Enhancement of insulin-dependent entry of glucose into cells Increased gluconeogenesis and glycogenolysis.

11. Physiological and metabolic effect B-Growth & Development Thyroid hormones necessary for normal growth in children as evidenced by the growth-retardation observed in thyroid deficiency . Normal levels of thyroid hormone are essential to the development of the fetal and neonatal brain. Lack of thyroid hormone during development results in short stature and mental deficits (cretinism). C-Other Effects Cardiovascular system : Thyroid hormones increases heart rate, cardiac output. They also promote vasodilation, which leads to enhanced blood flow to many organs. Central nervous system : Both decreased and increased concentrations of thyroid hormones lead to alterations in mental state. Reproductive system :. Hypothyroidism in particular is commonly associated with infertility .

12. TSH  FREE T4 FREE T3 PROBABLE INTERPRETATION High Normal Normal Mild (subclinical) hypothyroidism High Low Low Hypothyroidism Low Normal Normal Mild (subclinical) hyperthyroidism Low High High Hyperthyroidism Normal High High Thyroid hormone resistance syndrome (a  mutation  in the thyroid hormone receptor decreases thyroid hormone function)

13. Symptoms of hypothyroidism& hyperthyroidism

14. disease related to thyroid hormone THYROID GOITER A goiter is an abnormal enlargement of thyroid gland. The most common cause of goiters worldwide is a lack of iodine . During iodine deficiency, thyroid hormone production decreases. This results in increased TSH release. TSH acts on thyroid, increasing blood flow, and stimulating follicular cells and increasing colloid production. then thyroid gland enlarges.

15. disease related to thyroid hormone GRAVES' DISEASE is an autoimmune disorder in which antibodies against the TSH receptor act to stimulate the thyroid in the absence of TSH. ( hyperthyroidism) HASHIMOTO’S THYROIDITIS is an autoimmune disease in which the thyroid gland is attacked by a variety of cell- and antibody-mediated immune processes, causing primary ( hypothyroidism) This form of thyroid disease may also be referred to as chronic lymphocytic thyroiditis .