1 / 58

Diagnosis of Thyroid Disorders

Diagnosis of Thyroid Disorders. William Harper, MD, FRCPC Endocrinology & Metabolism Assistant Professor of Medicine, McMaster University www.drharper.ca. Case 1. 31 year old female Somalia  Canada 3 years ago G2P1A0, 11 weeks pregnant Well except fatigue Hb 108 , ferritin 7

kelsie-ball
Download Presentation

Diagnosis of Thyroid Disorders

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Diagnosis of Thyroid Disorders William Harper, MD, FRCPC Endocrinology & Metabolism Assistant Professor of Medicine, McMaster University www.drharper.ca

  2. Case 1 • 31 year old female • Somalia  Canada 3 years ago • G2P1A0, 11 weeks pregnant • Well except fatigue • Hb 108, ferritin 7 • TSH 0.2 mU/L, FT4 7 pM • Started on LT4 0.05  TSH < 0.01 mU/L FT4 12 pM, FT3 2.1 pM

  3. Case 1 • How would you characterize her hypothyroidism? • What are the ramifications of pregnancy to thyroid function/dysfunction?

  4. TSH Low High FT4 & FT3 FT4 Low Low High High Central Hypothyroid 1° Thyrotoxicosis 1° Hypothyroid If equivocal 2° thyrotoxicosis RAIU TRH Stim. • Endo consult • FT3, rT3 • MRI, α-SU MRI, etc.

  5. TRH Stimulation test A) 1° Hypothyroidism B) Central Hypothyroidism C) Euthyroid D) 1° Thyrotoxicosis

  6. Case 1 • GH, IGF-1 normal • LH, FSH, E2, progesterone, PRL normal for pregnancy • 8 AM cortisol 345, short ACTH test normal • MRI: normal pituitary • TGAB, TPOAB negative • LT4 increased until FT4 in hi-normal range • Normal pregnancy, delivery, baby, lactation • Considering TRH stim once done breast-feeding

  7. Thyroid Tests • Thyroid Function • Iodine Kinetics • Thyroid Structure • FNA • Thyroid Antibodies • Thyroglobulin

  8. Normal Daily Thyroid Secretion Rate: T4 = 100 ug/day T3 = 6 ug/day ( ratio T4:T3 = 14:1 ) T4 Protein* binding + 0.03% free T4 85% (peripheral conversion) T3 Protein* binding + 0.3% free T3 15% (10-20x less than T4) * TBG 75% TBPA 15% Albumin 10% Total T4 60-155 nM Total T3 0.7-2.1 nM T3RU/THBI 0.77-1.23

  9. Thyroid Function Tests TSH 0.4 –5.0 mU/L Free T4 (thyroxine) 9.1 – 23.8 pM Free T3 (triiodothyronine) 2.23-5.3 pM

  10. TSH Assay(0.4-5 mU/L) • Early RIA < 1.0 mU/L • Thyrotoxicosis / 2º hypothyroidism • Unable to detect lower range of normal • Monoclonal SEN < 0.1 mU/L • Super SEN < 0.01 mU/L

  11. Case 1 • How would you characterize her hypothyroidism? • What are the ramifications of pregnancy to thyroid function/dysfunction?

  12. Thyroid & Pregnancy: Normal Physiology • Increased estrogen  increased TBG • Higher total T4, T3 (normal FT4, FT3 if thyroid gland working properly) • hCG peak end of 1st trimester, weak TSH agonist so may cause slight goitre • Fetal thyroid starts working at 11 wks • T4 & T3 do NOT cross placenta (or do so minimally) • Do cross placenta: PTU, MTZ, TSH-R Ab (stim or block) • MTZ  aplasia cutis scalp defects

  13. Thyroid & Pregnancy: Hypothyroidism • Will need ~ 25% increase in LT4 during pregnancy due to increased TBG levels • Risks: increased spont abort, HTN, preterm pregnancy, 7 IQ points for fetus (NEJM, 341(8):549-555, Aug 31, 2001)

  14. LT4 dose adjustment in Pregnancy:Need TSH at baseline & q2mos while pregnantStarting LT4: 2 ug/kg/d and check TSH q4wk until euthythyroid

  15. Thyrotoxicosis & Pregnancy • Risks: fetal anomalies, spont abort, preterm labor, fetal hyperthyoridism, thyroid storm in labor • No RAI ever • Rx options: ATD or 2nd trimester thyroidectomy • PTU drug of choice (avoid MTZ due to scalp defects) • Aim to keep FT4 levels in hi normal range • OK to breast feed on PTU as does not go into breast milk

  16. Postpartum Thyroiditis • 5% (3-16%) postpartum women (25% T1DM) • Up to 1 year postpartum (most 1-4 months) • Lymphocytic infiltration (Hashimoto’s) • Postpartum  Exacerbation of all autoimmune dx • 25-50% persistant hypothyroidism • Small, diffuse, nontender goitre • Transiently thyrotoxic  Hypothyroid

  17. Postpartum Thyroiditis • Rx: • Hyperthyroid symptoms: atenolol 25-50 mg od • Hypothyroid symptoms: LT4 50-100 ug/d to start • Adjust LT4 dose for symptoms and normalization of TSH • Consider withdrawal at 6-9 months (25-50% persistent hypothyroid, hi-risk recur future preg)

  18. Postpartum & Thyroid • Postpartum depression • When studied, no association between postpartum depression/thyroiditis • Overlapping symtoms, R/O thyroid before start antidepressents • Screening for Postpartum Thyroiditis HOW: TSH q3mos from 1 mos to 1 year postpartum? WHO: • Symptoms of thyroid dysfn. • Goitre • T1DM • Postpartum thyroiditis with prior pregnancy

  19. Case 2 • 47 year old female • Concerned about weight gain over past 15 years (15 lbs). Otherwise asymptomatic • BMI 25, Thyroid: 40 gm, rubbery firm. • TSH 6.7 mU/L, FT4 13 pM, FT3 2.5 pM • FHx: mother, sister – both on LT4 • Medications: “Thyrosol” (health store) • Wondering about hypothyroidism causing her weight gain • Read on internet about “Wilson’s Disease”

  20. Case 2 • When to treat “Subclinical” thyroid dysfunction? • Naturopathic thyroid remedies • Hypothryoidism Rx other than Levothyroxine • What is Wilson’s Thyroid Disease?

  21. Subclincal Hypothyroidism •  TSH, normal FT4 • Most asymptomatic & don’t need Rx (monitor TSH q2-5y) • Rx Indications: • Increased risk of progression • TSH > 10, Female > 50 y.o. • Anti-TPO Ab titre > 1:100,000 ? • Goitre present ? • Dyslipidemia? • Total cholesterol (TC)  6-8% if TSH > 10 and TC > 6.2 nM • Symptoms? • Pregnancy, Infertility, Ovulatory Dysfn.

  22. Subclinical Hyperthyroidism •  TSH, Normal FT4 and FT3 • Progression to overt hyperthyroidism low: • Men 0% per year • Women 1.5% per year • TMNG or toxic adenoma present 5% per year • Indications to Rx: • Any cardiac disease (CAD, AFIB, etc.) • Age > 60 (10 year risk AFIB 32%, 10% if normal TSH) • TMNG or toxic adenoma • Osteoporosis

  23. Case 2 • When to treat “Subclinical” thyroid dysfunction? • Naturopathic thyroid remedies (Thyrosol) • Hypothryoidism Rx other than Levothyroxine • What is Wilson’s Thyroid Disease?

  24. Hashimoto’s Disease • Most common cause of hypothyroidism in North America (not idodine defeciency!) • Autoimmune • lymphocytic thyroiditis • Females > Males, Runs in Families • Antithyroid antibodies: • Thyroglobulin Ab • Microsomal Ab • TSH-R Ab (block)

  25. Hashimoto’s Disease • Treatment: • Thyroid Hormone Replacement • Levothyroxine (T4) • T3?, T4/T3 combo?, dessicated thyroid? • No benefit to giving iodine! • In fact, iodine may decrease hormone production • Wolff-Chaikoff effect (lack of escape)

  26. Case 2 • When to treat “Subclinical” thyroid dysfunction? • Naturopathic thyroid remedies • Hypothryoidism Rx other than Levothyroxine • What is Wilson’s Thyroid Disease?

  27. Treatment of Hypothyroidism • Iodine only if iodine deficiency is the cause • Rare in North America! • Replacement thyroid hormone medication: • T4? • T3? • T4 + T3 Mixture? • Thyroid Hormone from “natural sources” ?

  28. Normal Daily Thyroid Secretion Rate: T4 = 100 ug/day T3 = 6 ug/day ( ratio T4:T3 = 14:1 ) T4 Protein* binding + 0.03% free T4 85% (peripheral conversion) T3 Protein* binding + 0.3% free T3 15% (10-20x less than T4)

  29. Levothyroxine (T4) • Synthroid (Abbott), Eltroxin (GSK) • Synthetically made • 50 ug white pill  no dye (hypoallergenic) • Most commonly prescribed treatment for hypothyroidism • No T3 (but 85% of T3 comes from T4 conversion) • All patients made euthyroid biochemically • Most (but not all) patients feel normal

  30. Levothyroxine (T4) • Average dose 1.6 ug/kg • Age > 50-60 or cardiac disease: must start at a low dose (25 ug/d) • Recheck thyroid hormone levels every 4-6 weeks after a dose change • Aim for a normal TSH level

  31. “I still don’t feel normal on Synthroid even though my blood tests are normal.” • Free T4, Free T3 • wide range of normal • TSH (0.4 –5.0 mU/L) • Narrow range of normal, but still a range! • Adjust dose for a lower TSH still in the normal range? • Tissue levels versus circulating levels? • No human studies • Rodents: High T4 and normal T3 tissue levels

  32. Liothyronine (T3) • Cytomel (Theramed) • Shorter half-life • Fluctuating levels (i.e. need a slow-release pill) • Twice daily dosing often needed • 10x more potent: palpitations & other cardiac side effects • High T3 levels, low T4 levels (not physiologic either!)

  33. T3/T4 Liotrix • Thyrolar • Combo pill of T3 and T4 • Ratio of T4:T3 = 4:1 (not 14:1) • T3 still not slow release • Few small studies showing benefit • 1999 NEJM study 33 patients • Benefit: mood & cognitive function • Not available in Canada

  34. Desiccated Thyroid (Armour) • Desiccated powder derived from thyroids of slaughtered pigs or cows • Vegetarian? • Mad Cow Disease? • Contains T4 and T3 • Still no slow-release of T3 • Ratio of T4:T3 • Variable • Still not physiologic, often too high in T3 (T4:T3 = 3:1)

  35. “In an ideal world…” • Mixed compound with T4:T3 = 14:1 • T3 component slow release formulation • Resultant: • Normal circulating TSH, FT4, FT3 • Normal tissue levels of T4 and T3 • Good, large studies (RCTs) demonstrating clear benefit over T4 alone

  36. Case 2 • When to treat “Subclinical” thyroid dysfunction? • Naturopathic thyroid remedies • Hypothryoidism Rx other than Levothyroxine • What is Wilson’s Thyroid Disease?

  37. “Wilson’s Syndrome” • Wilson’s disease: copper toxicity  liver failure • “Wilson’s Syndrome” • Dr. E. D. Wilson “discovered” this condition and named it after himself in late 1980’s • Decreased body temperature (low normal range) • Hypothyroid symptoms (nonspecific) • Normal thyroid function tests • “Impaired T4  T3 conversion” • “Build up of reverse T3” • Treat with “Wilson’s T3-therapy” (presumably T3)

  38. Sick Euthyroid Syndrome, not Wilson’s syndrome!

  39. “Wilson’s Syndrome” • No scientific evidence that this condition exists • No randomized trials proving safety or any benefit of giving people T3 when their thyroid hormone levels are normal • This condition not endorsed by: • Canadain Society of Endocrinology and Metabolism (CSEM) • American Thyroid Association (ATA) • Endocrine Society

  40. Case 4 • 29 year old female, engaged to be married • T1DM • Thyroid U/S: • 2.9 cm R lower pole • 2.0 cm L lower pole, • Many others ranging from 0.5-1.5 cm • TSH < 0.05 mU/L, FT4 19 pM, FT3 6.9 pM • RAIU/Scan: 45% RAIU, hot nodule on Left

  41. Case 4 • FNA of 3cm nodule on Right: benign • Rx’s offered: • RAI ablation versus thyroidectomy • Patient chose Thyroidectomy

  42. RAIU • Oral dose of I131 5 uCi (or I123 200 uCi but more $) • Measure neck counts @ 24h (+/- 4h if suspect high turnover) • RAIU = neck counts – bkgd (thigh counts) x 100 pill counts - bkgd

  43. RAIU • Normal 4h RAIU = 5-15 % • 24h RAIU: >25% Hyperthyroid 20-25% Equivocal (check TSH) 9-20% Normal 5-9% Equivocal (check TSH) <5% Hypothyroid • Dependent on dietary iodine intake! • Must be: not pregnant! (ß-hCG), no ATD x 7d, no LT4 x 4d, no large doses of iodine or radiocontrast for 2 wk (prefer 4-6 wk)

More Related