Laboratory test The Thyroid gland ANIK WIDIJANTI Clinical Pathology Department Saiful Anwar Hospital / Medical Faculty Brawijaya University MALANG

ROUTINE LABORATORY EVALUATION TSH : Thyroid stimulating hormone Thyroxine (T4) and Triiodothyronine (T3) (free / total) ETIOLOGY TEST OF THYROID DYSFUNCTION Autoimmune thyroid disease is detected by circulating antibodies against TPO and Tg. As antibodies to Tg alone is uncommon, it is reasonable to measure only TPO antibodies

Characteristics of Circulating T4 and T 3 Hormone property T4 T 3 Total serum concentrations 8µg/dl 0.14 µg/dl Fraction of total hormone in free form (serum) 0.02 % 0.3 % Free (unbound hormone) in serum 21 X 10-12 M 6 X 10-12 M Serum half life 7 d 0.75 d Fraction directly from the thyroid 100 % 20 % Production rate, including peripheral conversion 90 µg/d 32 µg/d Intracellular hormone fraction ~ 20 % ~ 70 % Relative metabolic potency 0.3 1 Receptor binding 10-10 M 10-11 M

Measure TSH Elevated Normal Measure unbound T4 Pituitary disease suspected Normal Low No yes Primary hypothyroidism No further test Measure unbound T4 Mild hypothyroidism TPO Ab (+) TPO Ab (-) Low Normal TPO Ab (+) or symptomatic TPO Ab (-) or no symptoms No further test Rule out other Causes of hypothyroidism Autoimmun hypothyroidism Rule out drug effects, sick Euthyroid syndrome, then Evaluate anterior pituitary function T4 treatment Annual follow up T4 treatment

Aplication of TSH Examination BIOASSAY VARIATION OF SENSITIVITY : INCONVINIENT RIAs SENSITIVITY 1mU/L CROSS REACTION < 1 % HYPOTHYROID IRMAs SENSITIVITY 10 - 200 X RIAs HYPO + EUTTHROID HYPERTIHYROID TSH 0.05 - 0. 11mU/L EUTHYROID 0.4 - 4.0 HYPOTHYROID 4 m U/L I II Detection ICMAs < 0.1 IMMUNO ASSAY I : 5 – 7 m U/L IMMUNO ASSAY III : 0.01 – 0.02 II : O.1 – 0.2 IV : 0.001 – 0.002

THYROID AUTOIMUN (AIT) Anti Tg Sitoplasma folikular Complement activation (-) Anti TPO 105 kd, mikrosomal Thyroid peroksidase enzyme Korelasi (+) anti TPO & PPTD Complement activation (+) AntiTSH-R  hypertiroid  hypotiroid !! in GD Ab bispesifik :Ab TPO more frequent & higher than anti Tg, Only Anti TPO (+) : rare Anti TPO & anti Tg pd GD : not establish (discussion) Routin Deteksion Ab tiroid : only anti TPO

Prevalensi anti TPO Ab bispesifik Anti TPO & AIT PPTD (post partum thyroiditis) : 16 % Grave disease : 34,6 % Hasimoto thyroiditis : 40.5 % Ab bispesifik PPTD : 16 % N population : 1,4 % Anti TPO & AIT Clinical relevancy : not clearly Correlation with active clinical disease Strong correlation with risk of PPTD

Anti TPO for predict PPTD Variation of sensitivity & spesificity Depend on when anti TPO examined PPTD (-) when anti TPO (-)  Screening anti TPO in early pregnancy

Anti Tg Tiroglobulin (Tg) Jodium Defisiensi IHA > 1 : 1000 Prekursor thyroid H Produced in thyroid gland Secretion to colloid Thyroid H reserved Reseptor apical Tg for traffic Tg intraselular Early indikator PPTD Rise in GD Target anti Tg Anti Tg Jodium Defisiensi Detection AIT (Goiter +) Monitoring jodium Tx IHA > 1 : 1000 T Hasimoto : 80 % GD : 60 % Tiroid carcinoma: 30 % IHA < 1 : 1000 Normal : 3-18 % Anemia Pernisiosa Syogren Syndrome

SERUM Tg EXAMINATION Not distinguish : PPTD & GD Interferens : serum anti Tg (reaction of anti Tg + anti Tg antibodi in immunoassay kit),  examination simultaneously Tg + anti Tg

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