WHO SHOULD BE TESTED FOR THYROID DYSFUNCTION? Groups with an increased likelihood of thyroid dysfunction Previous thyroid disease or surgery Goitre Associated autoimmune disease(s) Diabetes mellitus Previous postpartum thyroid dysfunction Down's syndrome Irradiation of head and neck Radical laryngeal/pharyngeal surgery Recent Cushing's syndrome Drug therapy Amiodarone Lithium Biological agents Interferon a Interferon b Interleukin 2 Therapeutic use of antibodies Pituitary surgery or irradiation Severe head injury Very low birth weight premature infants
BIOCHEMICAL TESTS TSH T4,T3 T3RU FREE T4 INDEX (FTI) FREE T4,FREE T3 Tg OTHERS rT3,iodothyroins,Triac,Tetrac,compound W,Urine Iodine
PHYSIOLOGIC CONTROL OF THYROID HORMONE PRODUCTION
TSH TSH Almost always = Thyroid hormones Rarely central hyperthyroidism Thyroid hormone resistance TSH Central hypothyroidism Thyrotoxicosis (clinical or subclinical) SES
The relationship between serum TSH and free T4 concentration is shown for normal subjects (N) and in the typical abnormalities of thyroid function: A, primary hypothyroidism ; B, central or pituitary-dependent hypothyroidism; C, thyrotoxicosis due to autonomy or abnormal stimulation of the gland; D, TSH-dependent thyrotoxicosis or thyroid hormone resistance. Note that linear changes in the concentration of T4 correspond to logarithmic changes in serum TSH.
T3RU It is an index of TBG If TBG T3RU If TBG T3RU T3RU * TOTAL T4 = FREE T4 INDEX