interpreting tfts

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Interpreting Interpreting Thyroid Function Thyroid Function Tests Tests DOMMR DOMMR Rozina Mithani Rozina Mithani

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Page 1: Interpreting TFTs

Interpreting Interpreting Thyroid Function Thyroid Function TestsTests

DOMMRDOMMR

Rozina MithaniRozina Mithani

Page 2: Interpreting TFTs

Pt Info:Pt Info: CC: palpitationsCC: palpitations

82 y/o F presents with hyperactivity, sweating, 82 y/o F presents with hyperactivity, sweating, palpitations, wt loss, insomnia, moist skin, fine palpitations, wt loss, insomnia, moist skin, fine hair, irregular menses, diarrheahair, irregular menses, diarrhea

PE: tachy, elevated SBP, damp skin, lid lag, PE: tachy, elevated SBP, damp skin, lid lag, hyperreflexive DTRhyperreflexive DTR

Labs: CBC wnl, BMP wnl, TSH <0.01 (L), T4 4.1 Labs: CBC wnl, BMP wnl, TSH <0.01 (L), T4 4.1 (H), T3 wnl(H), T3 wnl

Page 3: Interpreting TFTs

ObjectivesObjectives

PathophysiologyPathophysiology

ThyrotoxicosisThyrotoxicosis

HypothyroidHypothyroid

Page 4: Interpreting TFTs

Hormone RegulationHormone Regulation

TRH TRH TSH TSH iodine uptake, organificationiodine uptake, organification synthesis & release of thyroid hormonesynthesis & release of thyroid hormone

T4/T3 Regulate:T4/T3 Regulate: basal metabolism, thermogenesis, basal metabolism, thermogenesis,

lipogenesislipogenesis fetal CNS developmentfetal CNS development

Page 5: Interpreting TFTs

Thyroid HormonesThyroid Hormones

Thyroxine (T4)Thyroxine (T4) Thyroid glandThyroid gland t1/2: 8 dayst1/2: 8 days

Triiodothyronine (T3)Triiodothyronine (T3) 80% in Periphery80% in Periphery

Liver/kidney remove iodine from T4 Liver/kidney remove iodine from T4

Regulate Thyroid Hormone-Regulate Thyroid Hormone-dependent genesdependent genes

t1/2: 1-1.5 dayst1/2: 1-1.5 days

T4 T4 T3 T3 Decreased:Decreased:

Meds: propranolol, PTU, Meds: propranolol, PTU, corticosteroids, amiodaronecorticosteroids, amiodarone

Illness: cytokine mediatedIllness: cytokine mediated

Page 6: Interpreting TFTs

Binding ProteinsBinding Proteins

T4/T3 99% protein boundT4/T3 99% protein bound Prevents excess tissue uptakePrevents excess tissue uptake Maintains accessible reserveMaintains accessible reserve

Thyroxine-binding globulin (TBG) - 70%Thyroxine-binding globulin (TBG) - 70% Inc: E2, 5-FU, Methadone, TamoxifenInc: E2, 5-FU, Methadone, Tamoxifen Dec: Androgens, Corticosteroids, NiacinDec: Androgens, Corticosteroids, Niacin

Albumin – 15-20%Albumin – 15-20% Transthyretin – 10-15%Transthyretin – 10-15%

Page 7: Interpreting TFTs

TFTsTFTs

TSH

HIGH = HypoCheck free T4

NL =No further Testing

LOW = HyperCheck free T3/T4

Page 8: Interpreting TFTs

FunctionalDisorders

Thyrotoxicosis Hypothyroidism

-Grave’s Disease- Toxic Adenoma

- Toxic Multinodular Goiter-Thyroiditis-Exogenous

-TSH Mediated

-Hashimoto’s Disease- Post-op/Post-ablative

-I deficiency

Page 9: Interpreting TFTs

ThyrotoxicosisThyrotoxicosis

Thyroid excess from any cause:Thyroid excess from any cause: Increased SynthesisIncreased Synthesis Damaged Gland Damaged Gland Exogenous IntakeExogenous Intake

RAIURAIU High (>30%): HyperfunctionHigh (>30%): Hyperfunction NL (10-30%): EuthyroidNL (10-30%): Euthyroid Low (<10%): Thyroiditis, I excess, AmiodaroneLow (<10%): Thyroiditis, I excess, Amiodarone

Page 10: Interpreting TFTs

SymptomsSymptoms

Increased Metabolism:Increased Metabolism: Weight loss, Dec appetiteWeight loss, Dec appetite Warm, sweating, thirst, fever Warm, sweating, thirst, fever Tachycardia, Arrhythmia, Tachycardia, Arrhythmia,

PalpitationsPalpitations Diarrhea Diarrhea Fatigue, Exhaustion Fatigue, Exhaustion GoiterGoiter Difficulty concentratingDifficulty concentrating Panic and anxiety Panic and anxiety Hyperreflexia, Tremors Hyperreflexia, Tremors InsomniaInsomnia

Other:Other: Pregnancy-related problems Pregnancy-related problems Arthralgias Arthralgias Skin: hives, itching, vitiligoSkin: hives, itching, vitiligo Hair loss Hair loss Finger/nail changesFinger/nail changes Eye: bulging, dry, painEye: bulging, dry, pain Depression, irrational anger Depression, irrational anger

Page 11: Interpreting TFTs

ThyrotoxicosisThyrotoxicosis

Increased SynthesisIncreased Synthesis

Damaged Gland Damaged Gland

Exogenous IntakeExogenous Intake

Page 12: Interpreting TFTs

Increased Synthesis: Increased Synthesis: HyperthyroidismHyperthyroidism High T4 & Low TSHHigh T4 & Low TSH

Increased T4/T3 release:Increased T4/T3 release: Grave’sGrave’s Toxic MNGToxic MNG Toxic AdenomaToxic Adenoma

High RAIUHigh RAIU

Page 13: Interpreting TFTs

Grave’s DiseaseGrave’s Disease

Most common cause in USMost common cause in US AutoAb against TSH receptorAutoAb against TSH receptor

Diffuse Goiter, Thyrotoxicosis, High RAIUDiffuse Goiter, Thyrotoxicosis, High RAIU Thyroid Scan: Increased activityThyroid Scan: Increased activity Ophthalmopathy, Dermopathy, Ophthalmopathy, Dermopathy,

AcropathyAcropathy

Page 14: Interpreting TFTs

Grave’s Disease - Grave’s Disease - treatmenttreatment Medication: 50% remission @ 1 yearMedication: 50% remission @ 1 year

MethimazoleMethimazole PTUPTU BB while toxicBB while toxic

Radioactive Iodine AblationRadioactive Iodine Ablation Not for pts with severe ophthalmopathyNot for pts with severe ophthalmopathy

Surgical RemovalSurgical Removal

Page 15: Interpreting TFTs

Toxic Multinodular Toxic Multinodular GoiterGoiter Sporadic Goiter Sporadic Goiter Multinodular Multinodular

Euthyroid Euthyroid Subclinical Subclinical Overt Thyrotoxicosis Overt Thyrotoxicosis

Increased RAIU (autonomous production)Increased RAIU (autonomous production) Rest of Gland suppressedRest of Gland suppressed

Treatment: Radioactive IodineTreatment: Radioactive Iodine

Page 16: Interpreting TFTs

Toxic AdenomaToxic Adenoma

HOT Nodule: Autonomous functionHOT Nodule: Autonomous function Activating Mutation of TSH ReceptorActivating Mutation of TSH Receptor Size = Hormone productionSize = Hormone production

>3 cm >3 cm

Treatment: Treatment: HemithyroidectomyHemithyroidectomy Radioactive IodineRadioactive Iodine

Page 17: Interpreting TFTs

ThyrotoxicosisThyrotoxicosis

Increased SynthesisIncreased Synthesis

Damaged Gland Damaged Gland

Exogenous IntakeExogenous Intake

Page 18: Interpreting TFTs

Damaged GlandDamaged Gland

Low RAIULow RAIU

Subacute Thyroiditis: BB & NSAIDsSubacute Thyroiditis: BB & NSAIDs Firm & painful glandFirm & painful gland Post-viralPost-viral

Drug-InducedDrug-Induced Amiodarone, Lithium, Amiodarone, Lithium, αα-IFN, IL-2-IFN, IL-2

Postpartum ThyroiditisPostpartum Thyroiditis

Page 19: Interpreting TFTs

Amiodarone-InducedAmiodarone-Induced

3% of patients in US3% of patients in US Type 1: high iodine content (JodBasedow)Type 1: high iodine content (JodBasedow)

Pre-existing thyroid autonomyPre-existing thyroid autonomy High RAIUHigh RAIU Treatment: methimazoleTreatment: methimazole

Type 2: direct toxic effectType 2: direct toxic effect No Pre-existing thyroid autonomyNo Pre-existing thyroid autonomy Low RAIU, Inc InflammationLow RAIU, Inc Inflammation Treatment: Prednisone, NSAIDsTreatment: Prednisone, NSAIDs

Page 20: Interpreting TFTs

ThyrotoxicosisThyrotoxicosis

Increased SynthesisIncreased Synthesis

Damaged Gland Damaged Gland

Exogenous IntakeExogenous Intake

Page 21: Interpreting TFTs

Surreptitious IntakeSurreptitious Intake

Low TSHLow TSH Low RAIULow RAIU Low TG levelLow TG level

Page 22: Interpreting TFTs

Thyroid StormThyroid Storm

IatrogenicIatrogenic Radioiodine therapy, Contrast dyesRadioiodine therapy, Contrast dyes

Abrupt cessation of Antithyroid drugsAbrupt cessation of Antithyroid drugs SurgerySurgery Acute Nonthyroidal IllnessAcute Nonthyroidal Illness

Stroke, PE, DKA, Trauma, InfectionStroke, PE, DKA, Trauma, Infection

Page 23: Interpreting TFTs

Thyroid Storm - Thyroid Storm - treatmenttreatment

•Blocks T4T3Hydrocortisone/

Dexamethasone

•Blocks new hormone synthesis•Blocks hormone release

Iodine

•Blocks T4T3 in high dosesPropanolol/

Esmolol Infusion

•Blocks new hormone synthesis•Blocks T4T3

PTU/Methimazole

Drug

Page 24: Interpreting TFTs

Subclinical Subclinical ThyrotoxicosisThyrotoxicosis Low TSH & High NL T4Low TSH & High NL T4

ComplicationsComplications Arrhythmia, OsteoporosisArrhythmia, Osteoporosis esp >65y/o with TSH <0.1 mU/Lesp >65y/o with TSH <0.1 mU/L

Page 25: Interpreting TFTs

FunctionalDisorders

Thyrotoxicosis Hypothyroidism

-Grave’s Disease- Toxic Adenoma

- Toxic Multinodular Goiter-Thyroiditis-Exogenous

-TSH Mediated

-Hashimoto’s Disease- Post-op/Post-ablative

-I deficiency

Page 26: Interpreting TFTs

HypothyroidismHypothyroidism

Low T4 & High TSHLow T4 & High TSH

More common than ThyrotoxicosisMore common than Thyrotoxicosis

Treatment: Synthroid - goal TSH 1-2 mU/LTreatment: Synthroid - goal TSH 1-2 mU/L

Page 27: Interpreting TFTs

SymptomsSymptoms

Slow Metabolism:Slow Metabolism: Weight GainWeight Gain ConstipationConstipation Hypothermia/Cold Hypothermia/Cold

IntoleranceIntolerance Fatigued, LethargyFatigued, Lethargy Slow Movements/speechSlow Movements/speech Delayed DTRsDelayed DTRs BradycardiaBradycardia

Accumulation of Matrix Accumulation of Matrix Substance:Substance:

Skin: coarse/dry, scalySkin: coarse/dry, scaly Hair: coarse/dry, brittle, lossHair: coarse/dry, brittle, loss HoarsenessHoarseness Edema of eyes and faceEdema of eyes and face

Other:Other: ArthralgiasArthralgias Irregular menstrual cyclesIrregular menstrual cycles DepressionDepression

Page 28: Interpreting TFTs

Monitoring Monitoring ReplacementReplacement

TSH

HIGH = Not EnoughINC Dose

NL = Continue Dose

LOW = Too MuchDEC Dose

Page 29: Interpreting TFTs

Medication Medication ControversyControversy ? T3? T3

1999: improved mood 1999: improved mood & psych testing with & psych testing with combo therapycombo therapy

Four subsequent Four subsequent studies refutedstudies refuted

? Generic Synthroid? Generic Synthroid Not all bioequivalent Not all bioequivalent

when FDA approvedwhen FDA approved

Page 30: Interpreting TFTs

Hashimoto’sHashimoto’s

Most common cause in North AmericaMost common cause in North America Positive anti-TPO AbPositive anti-TPO Ab Increase Autoimmune EndocrinopathyIncrease Autoimmune Endocrinopathy

Addison’s, DM1, Premature ovarian failureAddison’s, DM1, Premature ovarian failure

No further w/uNo further w/u

Page 31: Interpreting TFTs

Myxedema ComaMyxedema Coma

Obtundation, HypothermiaObtundation, Hypothermia

CV Changes: CV Changes: Dec HR, Contractility, SBP, CODec HR, Contractility, SBP, CO Inc SVR, DBPInc SVR, DBP Pericardial EffusionPericardial Effusion

Precipitant: Infection, trauma, cold, sedativePrecipitant: Infection, trauma, cold, sedative

Page 32: Interpreting TFTs

Myxedema Coma - Myxedema Coma - treatmenttreatment IV Levothroxine replacementIV Levothroxine replacement Corticosteroids – adrenal insufficiencyCorticosteroids – adrenal insufficiency MV – CO2 retention, hypoxiaMV – CO2 retention, hypoxia Treat precipitating causeTreat precipitating cause

Page 33: Interpreting TFTs

Subclinical Subclinical HypothyroidismHypothyroidism High TSH & Low NL T4High TSH & Low NL T4 Most have Hashimoto’sMost have Hashimoto’s

Systemic symptoms, elevated LDL, Systemic symptoms, elevated LDL, Cardiac changesCardiac changes

Page 34: Interpreting TFTs

ObjectivesObjectives

PathophysiologyPathophysiology

ThyrotoxicosisThyrotoxicosis

HypothyroidHypothyroid