Thyroid Function Test_Nursing.pptx student

The best way to initially test thyroid function is to measure the TSH level in a blood sample. Changes in TSH can serve as an “early warning system.”

1. T hyroid F unction T est By. Mr. Abhijit Bhoyar 1

2. Specific Learning objectives At the end of the lecture students will be able to Describ e about thyroid Explain different function tests and interpret the findings of thyroid

3. INTRODUCTION Thyroid hormones: Tetra iodothyronine / thyroxine (T4) tri iodothyronine (T3) Binds to: thyroxine binding globulin (TBG) thyroxine binding pre albumin (TBPA) albumin apolipoproteins Free fractions are metabolically active

4. Thyroid gland (weighs about 30 g in adults) is located on either side of the trachea below the larynx. It produces two principal hormones —thyroxine (T4; 3,5,3’,5’-tetraiodothyronine) and 3,5,3’-triiodothyronine (T3)— which regulate the metabolic rate of the body. Thyroid gland also secretes calcitonin, a hormone concerned with calcium homeostasis (discussed under calcium metabolism)

5. Thyroid Definition A gland located beneath the larynx that makes thyroid hormone and calcitonin. The thyroid gland helps regulate growth and metabolism. Also called thyroid.

6. Biosynthesis of thyroid hormones Iodine is essential for the synthesis of thyroid hormones. More than half of the body’s total iodine content is found in the thyroid gland

7. Biochemical function of thyroid hormones Triiodothyronine (T3) is about four times more active in its biological functions than thyroxine (T4). The following are the biochemical functions attributed to thyroid hormones (T3 and T4). 1. Influence on the metabolic rate : Thyroid hormones stimulate the metabolic activities and increases the oxygen consumption in most of the tissues of the body. Na+-K+ ATP pump :

8. This is an energy dependent process which consumes a major share of cellular ATP. Na+-K+ ATPase activity is directly correlated to thyroid hormones and this, in turn, with ATP utilization. Obesity in some individuals is attributed to a decreased energy utilization and heat production due to diminished Na+-K+ ATPase activity.

9. 2 . Effect on protein synthesis : Thyroid hormones act like steroid hormones in promoting protein synthesis by acting at the transcriptional level (activate DNA to produce RNA). Thyroid hormones, thus, function as anabolic hormones and cause positive nitrogen balance and promote growth and development.

10. 3. Influence on carbohydrate metabolism : Thyroid hormones promote intestinal absorption of glucose and its utilization. These hormones increase gluconeogenesis and glycogenolysis , with an overall effect of enhancing blood glucose level (hyperglycemia). 4 . Effect on lipid metabolism : Lipid turnover and utilization are stimulated by thyroid hormones. Hypothyroidism is associated with elevated plasma cholesterol levels which can be reversed by thyroid hormone administration

11. Thyroid test Thyroxine (T4) Triiodotyronine (T3) Thyroid stimulating hormone (TSH) Free T4 Free T3 Free triiodothyronine (T3) — 80–220 ng/dl Free thyroxine (T4) — 0.8–2.4 ng/dl Total thyroxine (T4) — 5–12 Pg /dl Thyroid stimulating hormone (TSH) — 10mU/dl

12. Regulation of carbohydrate, lipid & protein metabolism. Central nervous system activity & brain development Cardiovascular stimulation Bone & tissue growth & development Gastrointestinal regulation

13. Synthesis & negative feedback regulation of thyroid hormones The tests used to investigate thyroid function can be grouped into: Tests that establish whether there is thyroid dysfunction: TSH, total T4 & total T3 measurements. Tests to know the cause of thyroid dysfunction: Thyroid auto-antibody Serum thyroglobulin measurements. Thyroid enzyme activities, biopsy of the thyroid, ultrasound & isotopic thyroid scanning

14. TSH: The single most sensitive, specific & reliable test of thyroid status. In primary hypothyroidism: TSH is increased. In primary hyperthyroidism: TSH is decrease or undetectable

15. Total T4 and Total T3: More than 99% of T4 & T3 circulate in plasma bound to protein Both TT4] & TT3] change if TBG alters, e.g. in pregnancy. Free T4 and Free T3: Free thyroid hormone concentrations are independent of changes in the concentration of thyroid-hormone binding proteins. More reliable for diagnosis of thyroid dysfunction.

16. Thyroid hormones are analyzed by: ELISA RIA Chemiluminescence Fluorescent immunoassay Primary hyperthyroidism: Plasma TSH: Decreased due to feedback inhibition on the pituitary gland. Plasma free & total T4 & T3 concentrations are increased

17. In a very small percentage of hyperthyroid patients, plasma total T4 & freeT4 are both normal, whereas both plasma total T3 & freeT3 are increased; this condition is known as T3 hyperthyroidism or T3 thyrotoxicosis.

18. Plasma TSH: Increased. Plasma free T4 & total T4: Decreased Plasma free T3 & total T3 measurements are of no value here, since normal concentrations are observed. Plasma TSH: Abnormal Thyroid hormone levels: Normal TSH : Low in sub clinical hyperthyroidism. TSH: Elevated in sub clinical hypothyroidism

19. Central (pituitary) hypothyroidism: TSH & thyroid hormone levels are low. Hyperthyroidism due to a TSH secreting tumor very rarely. Plasma TSH is widely used to screen for congenital hypothyroidism in the neonate. The incidence about one in 4000 live births .

20. Expected Question Essay / Situation Question Describe the thyroid function test Short Question Explain about thyroid. Explain T3 & T4test .

21. THANK YOU