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www.drsarma.in Thyroid Function Tests 1. TSH (normal range 0.3- 4.0 mU/L) 2. Free T4 (normal range 0.7- 2.1 ng/dL) 3. Free T3 (normal range 1.4 - 4.4 pg/dL) 4. Anti-Thyroid Antibodies (TPO Ab, TSI) 5. Nuclear Scintigraphy ( I123 or TC 99m) 6. FNAC of nodule 1 What tests should I order ? www.drsarma.in As per the Guidelines of the AACE and ATA, ITS 1. TSH alone if Hypothyroidism is suspected 2. TSH and Free T4 only if Hyperthyroidism is suspected or for routine evaluation 3. Free T3 if T3 toxicosis is suspected 4. For follow-up of treatment only TSH 5. Don’t order for Total T4 or Total T3 6. Never order RIU in pregnancy or lactation 2 FREE THYROXINE or FT4 NINE SQUARES MAJIC www.drsarma.in PRIMARY HYPERTHYROID NTI or Patient is on ELTROXIN SECONDARY HYPERTHYROID SUB-CLINICAL HYPERTHYROID EUTHYROID SUB-CLINICAL HYPOTHYROID SECONDARY HYPOTHYROID NON THYROID ILLNESS - NTI PRIMARY HYPOTHYROID NORMAL HIGH LOW THYROID STIMULATING HORMONE - TSH 3 www.drsarma.in The Commandments Suspect hypothyroidism ever All obese patients TSH a must Growth and pubertal delay For all pregnant -test TSH, FT4 Unexplained depression Postmenopausal 15% Hypothy TSH is the test in Hypothy. Start low and go slow TSH, FT4 to confirm Dx. Use L-Thyroxine only Nine square magic Always on empty stomach Test cord blood for TSH Thyroxine - avoid empirical use 4 Algorithm for Hypothyroidism www.drsarma.in Measure TSH Elevated TSH Normal TSH Measure FT4 Considering Pituitary Normal Low Sub-clinical hypo TPO + T4 repl TPO Annual FU No Primary hypothyroid TPO - TPO + Hashimoto Others Yes No tests Low Evaluate Pituitary Sick Euthyroid Drugs effect Measure FT4 Normal No tests 5 Algorithm for Hyperthyroidism www.drsarma.in Measure TSH and FT4 TSH, FT4 N TSH, FT4 Primary (T4) Thyrotoxicosis TSH, FT4 Pituitary Adenoma Measure FT3 Features of Grave’s Yes Rx. Grave’s No RAIU Low RAIU Single Adenoma, MNG N TSH, FT4 N FNAC, N Scan High T3 Toxicosis Normal Sub-clinical Hyper F/u in 6-12 wks Sub Acute Thyroiditis, I2, ↑ Thyroxine6 www.drsarma.in Causes of Hyperthyroidism 1. Graves Disease – Diffuse Toxic Goiter 2. Plummer’s Disease – Toxic MNG 3. Toxic phase of Sub Acute Thyroiditis - SAT 4. Toxic Single Adenoma – STA 5. Pituitary Tumours – excess TSH 6. Molar pregnancy & Choriocarcinoma (↑↑ βHCG) 7. Metastatic thyroid cancers (functioning) 8. Struma Ovarii (Dermoid and Ovarian tumours) 9. Thyrotoxicosis Factitia ; INF, Amiodarone, SSRIs 7 www.drsarma.in Summary of Hyperthyroidism Hyperthyroidism Age % Enlarged Pain RAIU Treatment None ↑↑ ATD – 18 m ↑ RAI, Surgery ± RAI, ATD ↓↓ NSAID, Steroids. Graves (TSI Ab eye, dermo, bruit) 20 - 40 60% Diffuse Toxic MNG > 50 20% Lumpy Single Adenoma 35 - 50 5% Single None Any age 15% None Yes S Acute Thyroiditis Pressure TSH is markedly low, FT4 is elevated 8 www.drsarma.in Anti Thyroid Drugs (ATD) Imp. considerations Methimazole Propylthiouracil Efficacy Very potent Potent Duration of action Long acting BID/OD Short acting QID/TID In pregnancy Contraindicated Safely can be given Mechanism of action Iodination, Coupling Iodination, Coupling Conversion of T4 to T3 No action Inhibits conversion Adverse reactions Rashes, Neutropenia Rashes, ↑ Neutropenia Dosage 20 to 40 mg/ OD PO 100 to 150mg qid PO 9 Algorithm for Thyroid Nodule www.drsarma.in Thyroid Nodule Low TSH Normal TSH TC 99 Nuclear Scan Hot Nodule RAI Ablation, Surgery or ATD FNAC or US guided biopsy Cold Nodule 4% Malignant Surgery 10% 69% Suspicious or follicular Ca Benign T4 suppression Cyst 17% Non diagnostic – repeat FNAC Surgery or Cytology 10