Thyroid Function Tests

1. Thyroid Function Tests www.drsarma.in • TSH (normal range 0.3- 4.0 mU/L) • Free T4 (normal range 0.7- 2.1 ng/dL) • Free T3 (normal range 1.4 - 4.4 pg/dL) • Anti-Thyroid Antibodies (TPO Ab, TSI) • Nuclear Scintigraphy ( I123 or TC 99m) • FNAC of nodule

2. 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 T4only if Hyperthyroidism is suspected or for routine evaluation • 3. Free T3 if T3 toxicosis is suspected • 4. For follow-up of treatment only TSH • Don’t order for Total T4 or Total T3 • Never order RIU in pregnancy or lactation

3. www.drsarma.in NINE SQUARES MAJIC PRIMARY HYPERTHYROID NTI or Patient is on ELTROXIN SECONDARY HYPERTHYROID SUB-CLINICAL HYPERTHYROID SUB-CLINICAL HYPOTHYROID EUTHYROID FREE THYROXINE or FT4 LOW NORMAL HIGH SECONDARY HYPOTHYROID PRIMARY HYPOTHYROID NON THYROID ILLNESS - NTI LOW NORMAL HIGH THYROID STIMULATING HORMONE - TSH

4. www.drsarma.in The Commandments • All obese patients TSH a must • For all pregnant -test TSH, FT4 • Postmenopausal 15% Hypothy • Start low and go slow • Use L-Thyroxine only • Always on empty stomach • Thyroxine - avoid empirical use • Suspect hypothyroidism ever • Growth and pubertal delay • Unexplained depression • TSH is the test in Hypothy. • TSH, FT4 to confirm Dx. • Nine square magic • Test cord blood for TSH

5. Algorithm for Hypothyroidism www.drsarma.in Measure TSH Elevated TSH Normal TSH Measure FT4 Considering Pituitary Normal Low No Yes No tests Sub-clinical hypo Primary hypothyroid Measure FT4 TPO - TPO - TPO + TPO + Low Normal Hashimoto Evaluate Pituitary Sick Euthyroid Drugs effect T4 repl Annual FU No tests Others

6. Measure TSH and FT4  TSH, FT4 N  TSH,  FT4 N TSH, FT4 N  TSH,  FT4 FNAC, N Scan Primary (T4) Thyrotoxicosis Pituitary Adenoma Measure FT3 High T3 Toxicosis Features of Grave’s Normal Sub-clinical Hyper Yes No  RAIU Low RAIU F/u in 6-12 wks Rx. Grave’s Sub Acute Thyroiditis, I2, ↑ Thyroxine Single Adenoma, MNG www.drsarma.in Algorithm for Hyperthyroidism

7. Causes of Hyperthyroidism www.drsarma.in • Graves Disease – Diffuse Toxic Goiter • Plummer’s Disease – Toxic MNG • Toxic phase of Sub Acute Thyroiditis - SAT • Toxic Single Adenoma – STA • Pituitary Tumours – excess TSH • Molar pregnancy & Choriocarcinoma (↑↑ βHCG) • Metastatic thyroid cancers (functioning) • Struma Ovarii (Dermoid and Ovarian tumours) • Thyrotoxicosis Factitia ; INF, Amiodarone, SSRIs

8. Hyperthyroidism Age % Enlarged Pain RAIU Treatment Graves (TSI Ab eye, dermo, bruit) 20 - 40 60% Diffuse None ↑↑ ATD – 18 m Toxic MNG > 50 20% Lumpy Pressure ↑ RAI, Surgery Single Adenoma 35 - 50 5% Single None ± RAI, ATD S Acute Thyroiditis Any age 15% None Yes ↓↓ NSAID, Steroids. TSH is markedly low, FT4 is elevated Summary of Hyperthyroidism www.drsarma.in

9. Anti Thyroid Drugs (ATD) www.drsarma.in

10. Thyroid Nodule Low TSH Normal TSH TC 99 Nuclear Scan FNAC or US guided biopsy Hot Nodule Cold Nodule 4% 10% 69% 17% RAI Ablation, Surgery or ATD Non diagnostic – repeat FNAC Suspicious or follicular Ca Malignant Cyst Benign T4 suppression Surgery or Cytology Surgery www.drsarma.in Algorithm for Thyroid Nodule