copy of ent hypothyroidism
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Maryam Vasheghani , MD
Assistant Professor of Internal medicine _ EndocrinologistNational Research Institute of Tuberculosis and Lung DiseaseShahid Beheshti University of Medical Sciences, Tehran, Iran.
JULY 2015
HYPOTHYROIDISM
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AGENDA
• Thyroid Gland Anatomy Histology Thyroid Hormone Synthesis, Action and
Metabolism
• Hypothyroidism Epidemiology Clinical presentation Diagnosis Treatment
• Thyroid dysfunction management in patient who is candidate for surgery
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Thyroid Gland
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Thyroid Gland Histology
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Thyroid Hormone Synthesis, Metabolism, and Action
• I : IODINE TRAPPING • Iodide uptake is a critical first step (NIS & Pendrin)
• II : OXIDATION & ORGANIFICATION• The reactive iodine atom is added to selected tyrosyl
residues within Tg.
• III : COUPLING• The iodotyrosines in Tg are then coupled via an ether
linkage in a reaction that is also catalyzed by TPO• MIT + DIT = T3• DIT + DIT = T4
• IV : STORAGE• VI : RELEASE
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Regulation of Thyroid Hormone Synthesis
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Worldwide Iodine Nutrition
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HYPOTHYROIDISM
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DEFINITION
Hypothyroidism is a disorder with multiple causes in which the thyroid fails to secrete an adequate amount of thyroid hormone.
The most common thyroid dysfunction.
Tissue resistance to thyroid hormone:Rare
• Nygaard B.Primary hypothyroidism.Am Fam Physician. 2015 Mar 15;91(6):359-60.PMID: 25822552• Hennessey JV, Espaillat R. Subclinical hypothyroidism: a historical view and shifting prevalence. Int J Clin Pract. 2015
Jul;69(7):771-82. doi: 10.1111/ijcp.12619. • Lane LC, CheethamT, Congenital hypothyroidism – what is new?Paediatrics and Child Health. 2015 Jul ;25( 7): 302-307.
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CLASSIFICATION• There is different classification:
Congenital or AcquiredPrimary, Secondary or TertiaryOvert or Subclinical Transient or Permanent
• Webb EA, Dattani MT. Understanding hypopituitarism. Paediatrics and Child Health.2015 Jul;25(7 (295-301.
• Doggui, Radhouene; El Atia, Jalila. Iodine deficiency: Physiological, clinical and epidemiological features, and pre-analytical considerations.Annals of Endocrinology . 2015Jul; 76( 1):59-66. © 2015.
• Huang, Chun-Jui; Jap, Tjin-Shing. A systematic review of genetic studies of thyroid disorders in Taiwan.Journal of the Chinese Medical Association. 2015March; 78( 3): 145-153
• Gong G, Basom J. Mattevada S, Onger F. Association of hypothyroidism with low-level arsenic exposure in rural West Texas. Environ Res.2015 Apr;138:154-60. doi: 10.1016/j.envres.
• Zimmermann, Michael B, Prof; Boelaert, Kristien, MD. Iodine deficiency and thyroid disorders.The Lancet Diabetes & Endocrinology.2015; 3( 4): 286-295.
• Peckham S,Lowery D, Spencer S . Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water.
• J Epidemiol Community Health. 2015 Jul;69(7):619-24. doi: 10.1136/jech-2014-204971.
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ETHIOLOGY
Primary Secondary
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• Insufficient functioning thyroid tissue Autoimmune hypothyroidism
• Hashimoto's or atrophic thyroiditis Iatrogenic
• 131 I treatment, Thyroidectomy, • External irradiation of neck
Infiltrative destruction of thyroid tissue• Amyloidosis, Sarcoidosis, Hemochromatosis,
Scleroderma, Cystinosis, Riedel’s thyroiditis• Impaired thyroid hormone synthesis
Iodine deficiency Overexpression of type 3 deiodinase in infantile
hemangioma and other tumors Drug
• Iodine excess (e.g. iodine-containing contrast media and amiodarone), Lithium, Antithyroid drugs, PAS, INF-α, Aminoglutethimide, TK inhibitors (e.g., sunitinib)
• Hypopituitarism: Tumors Surgery Irradiation infiltrative disorders Sheehan’s syndrome Trauma genetic forms
• Isolated TSH deficiency or inactivity
• Bexarotene treatment• Hypothalamic disease:
Tumors Trauma Infiltrative disorders Idiopathic
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ETHIOLOGY CONT…
Transient Congenital
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• Thyroiditis Silent or postpartum Sub-acute
• Withdrawal of supra-physiologic thyroxin treatment
• Iatrogenic After 131I treatment or subtotal
thyroidectomy for Graves’ disease
• Hypopituitarism: Tumors, surgery or irradiation,
infiltrative disorders, Sheehan’s syndrome, trauma, genetic forms
• Isolated TSH deficiency or inactivity
• Bexarotene treatment• Hypothalamic disease:
Tumors, trauma, infiltrative disorders, idiopathic
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EPIDEMIOLOGY
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• Congenital hypothyroidism occurs in about 1 in 4000 newborns.
• Primary hypothyroidism prevalence ~ 5% of individuals.
• Mild or subclinical hypothyroidism prevalence ~ 15% 6–8% of women (10% over the age of 60)
and 3% of men.
• More common in women. (F/M = 4/1)
• The prevalence of overt hypothyroidism increases with age.
• The annual risk of developing clinical hypothyroidism is about 4% when subclinical hypothyroidism is associated with positive TPO antibodies.
• Secondary hypothyroidism is rare, representing less than 1% of cases.
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Congenital Hypothyroidism
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• Rare• Absent thyroid tissue or hereditary defects in
TH synthesis• Mental retardation due to lack of T4 • It may be associated with:
Autoimmune diseases (Diabetes Mellitus) Cardiomyopathy & CHD Galactorrhoea Muscular dystrophy + pseudohypertrophy (Kocher-
Debre-Semelaigne
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Department of Pediatrics, Division of Endocrinology, Oregon Health & Science University, 707 SW Gaines Street, Portland, OR, USA. Congenital hypothyroidismRastogi MV, LaFranchi SH - (2010)
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1717Prior to Therapy 7 months after therapy
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Diagnosis of CH
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1) Azizi F, Janghorbani M, Hatami H, editors. Epidemiology and Control of Common Diseases in Iran. 3rd Ed.Khosravi Publ; 2000. p. 123-39.2) Azizi F, Sheikholeslam R, Hedayati M, Mirmiran P, Malekafzali H, Kimiagar M, et al. Sustainable control ofiodine deficiency in Iran: beneficial results of the implementation of mandatory law on salt iodization. J EndocrinolInvest 2002; 25: 409-13.3)Azizi F, Mehran L, Sheikholeslam R, Ordookhani A,Naghavi M, Hedayati M, et al. Sustainability of a wellmonitored salt iodization program in Iran: marked reduction in goiter prevalence and eventual normalization of urinary iodine concentrations without alteration in iodine content of salt. J Endocrinol Invest 2008; 31: 422-31. 4) Delshad H, Amouzegar A, Mirmiran P, Mehran L, Azizi F. Eighteen years of continuously sustained elimination of iodine deficiency in the Islamic Republic of Iran: thevitality of periodic monitoring. Thyroid 2012; 22: 415-215) Veisani Y, Sayehmiri K, Rezaeian S, Delpisheh A .Congenital Hypothyroidism Screening Program in Iran; a Systematic Review and Metaanalysis. Iran J Pediatr.,201DEC 2014December; 24(6): 665–672.
Dr. MVasheghani
• In 2001 vs 1996 Total goiter rates were 13.9 vs 53.8%, (p<0.0001). Median (range) UIC in 2001 was 165 microg/l and in 1996 was 205 microg/l
(p<0.0001). 1• The goiter rate in the country was 6.5% . The total goiter rate in Hamedan,
Zanjan, Kermanshah, Mazandaran, and Gilan provinces was over 10%.2• According to Meta analysis the overall incidence of Congenital hypothyroidism
was 2/1000 in Iran (95% CI: .002 – .002).3• Elevated TSH levels and low TSH values were found in 8.1% and 3.4% of the
participants respectively. Among those with increased serum TSH, 5.7% had levels between 5.2 – 10 mIU/L and 2.4% had values greater than 10 mIU/L.4
• Congenital hypothyroidism is more prevalent in iran (2/1000 live births) .5
Epidemiology of Hypothyroidism in IRAN
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Karimi F, Kalantarhormozi MR, Dabbaghmanesh MH, Ranjbar Omrani G.Thyroid disorders and the prevalence of antithyroid antibodies in Shiraz population Arch Iran Med. 2014 May;17(5):347-51. doi: 0141705/AIM.008.
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Karimi F, Kalantarhormozi MR, Dabbaghmanesh MH, Ranjbar Omrani G.Thyroid disorders and the prevalence of antithyroid antibodies in Shiraz population Arch Iran Med. 2014 May;17(5):347-51. doi: 0141705/AIM.008.
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Thyroid Disease Spectrum
0 105
TSH, IU/mL
Subclinical HypothyroidismTSH >4.7 IU/mL, Free T4 Normal
Overt HypothyroidismTSH >4.7 IU/mL, Free T4 Low
EuthyroidTSH 0.5-4.7 IU/mL, Free T4 Normal
HyperthyroidismTSH <0.5 IU/mL, Free T3/T4 Normal or Elevated
Braverman LE, et al. Werner & Ingbar’s The Thyroid. A Fundamental and Clinical Text. 8th ed. 2000.Canaris GJ, et al. Arch Intern Med. 2000;160:526-534.
Vanderpump MP, et al. Clin Endocrinol (Oxf). 1995;43:55-68.Dr. MVasheghani
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EVALUATION• History & Physical Examination• Measurement of Thyroid Hormones
TSH assays Total T4 and total T3
Unbound thyroid hormones T3RU
• ↑ T3RU in hyperthyroidism and ↓ TBG Free T3 or free T4 index = total T4 or T3 concentration
x the thyroid hormone binding ratio (THBR)• Tests to Determine the Etiology
Antibodies against TPO and Tg ,TSI Serum Tg
• Radioiodine Uptake and Thyroid Scanning• Thyroid Ultrasound• Fine-Needle Aspiration (FNA) biopsyDr. MVasheghani 23
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Thyroid-Stimulating Hormone Assays
Ladenson PW, et al. Arch Intern Med. 2000;160:1573-1575.Braverman LE, et al. Werner & Ingbar’s The Thyroid. A Fundamental and Clinical Text. 8th ed. 2000.Zophel K, et al. Nuklearmedizin. 1999;38:150-155.Dr. MVasheghani
• Key test for diagnosis of hypothyroidism and hyperthyroidism
• TSH assay sensitivity has improved with subsequent test generations First generation: RIA
• Sensitivity: 1.0 IU/mL Second generation: IRMA
• Sensitivity: 0.1 IU/mL Third generation: ELISA
• Sensitivity: 0.03 IU/mL Chemiluminescence immuno assay : CLIA
• Gold standard ,Sensitivity: 0.001 IU/mL
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What the mind knows the What the mind knows the eyes see !!eyes see !!
• Other Autoimmune disease
• Rx. Grave’s Ophthalmopathy
• Family Hx. thyroid disease
• Neck irradiation therapy
• Previous Rx for thyrotoxicosis
• Autoimmune Thyroiditis
• Chronic urticaria
Order for TSH alone as a screen test
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• Psychiatric patients
• Elderly women / men
• Patients of OSA
• Hypercholesterolemia
• Lithium, Amiodarone
• Postpartum women
Caraccio N, et al. J Clin Endocrinol Metab. 2002;87:1533-1538.Carmel R, et al. Arch Intern Med. 1982;142:1465-1469.Perros P, et al. Diabetes Med. 1995;12:622-627.
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Screening for Disorders of Thyroid Function
DisorderPrevalence in AdultsScreening Recommendation
Hypothyroidism5–10%, women0.5–2%, men
TSH; confirm with free T4 Screen women after age 35 and
every 5 years thereafter
Graves’ disease1–3%, women
0.1%, menTSH, free T4
Thyroid nodules and neoplasia
2–5% palpable>25% by ultrasound
Physical examination of thyroidFine-needle aspiration biopsy
Hyperparathyroidism0.1–0.5%,
women > men
Serum calcium PTH, if calcium is elevated
Assess comorbid conditions
Table 399-2 The Principle of Internal Medicine, Harrison 19 th editionDr. MVasheghani26
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Autoimmune Hypothyroidism
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Hashimoto's thyroiditis (chronic autoimmune thyroiditis) is the most common cause of hypothyroidism in iodine-sufficient areas of the world. It is characterized clinically bygradual thyroid failure, goiter, or both, due to autoimmune-mediated destruction of the thyroid gland. Nearly all patients have high serum concentrations of antibodies againstone or more thyroid antigens, lymphocytic infiltration of the thyroid, which includes thyroid-specific B and T cells, and apoptosis of thyroid follicular cells.
Chronic Autoimmune Thyroiditis
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Grave’s Disease Hashimoto Disease
Postpartum thyroiditis
Silent thyroiditis
Drug induced thyroiditis
Spectrum of thyroid autoimmunity
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Possible precipitating factors
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• Genetic
• Gender: Women have more risk.
• Age: Elderly
• Infection
• Stress
• Humoral factors (sex steroids , pregnancy)
• Prior history of Graves disease or postpartum thyroid dysfunction
• Other autoimmune disease Pernicious anemia Type 1 Diabetes mellitus
• Family history of thyroid disease other autoimmune disease• Laboratory evidence of hypercholesterolemia, elevated LFTs,
elevated CPK and LDH
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Pathogenesis
Molecular mimicryBystander activationThyroid cell expression of HLA AgThyroid cell apoptosis
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• Thyroid auoantigenes• Role of B cells• The primary role of T cells• Potential mechanism of thyroid
injury
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•The disease clusters in families, sometimes alone and sometimes in combination with Graves' disease • It is more common in women.• The concordance rate in monozygotic twins is 30 to 60 percent. • It occurs with increased frequency in patients with Down's and Turner's syndrome.• There is an association, albeit relatively weak, with certain HLA alleles.• There is an association with certain alleles of the gene for CTLA-4, a T-cell surface molecule
involved in T-cell activation Dr. MVasheghani
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TFT in Progressive Hypothyroidism
TSH
Moderate SevereMild
Normal Range
Free T4Free T3
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The characteristic histopathological abnormalities are profuse lymphocytic infiltration, lymphoid germinal centers, and destruction of thyroid follicular cells .fibrosis and areas of follicular-cell hyperplasia, presumably induced by TSH, are also seen in patients with severe disease. The intrathyroidal lymphocytes are both T and B lymphocytes.
PATHOLOGY
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Clinical Features of Hypothyroidism
• Hypothyroidism is insidious in onset and the most of symptoms or signs are nonspecific in nature, these make it difficult to diagnose. Symptoms that are new, progressive, or present in combination are more likely to be due to hypothyroidism.
• Moreover, hypothyroidism S&S vary according to the age at onset and disease severity.
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CURRENT CLINICAL PICTURE
• The prevalence of hypothyroid patients presenting with minimal symptoms is increased, largely due to the availability of sensitive and specific laboratory tests that allow recognition of the primary form of the disease long before severe symptoms have developed.
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Figure 12-5 Frequency of hypothyroid symptoms and signs (%) overt hypothyroidism and controls
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Causes of clinical S & S• The mechanisms of S & S are:
Slowing of metabolic process Accumulation of matrix substance
• The clinical features of disease are the consequence of: Thyroid hormone deficiency Thyroid autoimmunity Associated with signs or symptoms of other
autoimmune diseases, particularly Vitiligo, PA, Addison’s disease, Alopecia areata, and T1DM
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Multisystem effects of Hypothyroidism
• GeneralTirednessWeakness and FatigueCold Intolerance (Feeling cool)Lethargy, SomnolenceWeight gain with poor appetite
• The weight gain is usually modest and due mainly to fluid retention in the myxedematous tissues.
• Typical features (myxedema) include a puffy face with edematous eyelids and nonpitting pretibial edema .
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Skin and Hair
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• Thickening, flayking and dryness of skin Decreased sweating
Thinning of the epidermis
Hyperkeratosis of the stratum corneum.
Increased dermal glycosaminoglycan (myxedema)
Content traps water, giving rise to skin thickening without pitting
• Dry, coarse hair, Alopecia
• Loss of lateral eyebrow hair (thinning of the outer third of the eyebrows)
• Pallor, often with a yellow tinge to the skin due to Carotenimia.
• Nail growth is retarded and brittle.
• Blood flow is diverted from the skin, producing cool extremities. Myxoedema, Malar flushes, Vitiligo
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Head and Neck
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• Impaired hearing due to Conductive deafness
• Hoarse voice• Thick, slurred (clumsy) speech and are
due to myxedematous infiltration of the tongue and larynx, respectively.
• Ophthalmopathy occurs in about 5% of pts with autoimmune hypothyroidism
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Cardiovascular
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• Dyspnea, Angina • Decreased ventricular contractility, CHF• Increased diastolic blood pressure• Narrow pulse pressure
Reduced stroke volume Increased peripheral resistance
• Bradycardia• Peripheral non-pitting edema
• Pericardial effusions occur in up to 30% of patients but rarely compromise cardiac function.
• Alterations in myosin heavy chain isoform expression have been documented ,but cardiomyopathy is unusual.
• HyperlipIdemia, Xanthelsma
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Respiratory system
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• Pulmonary function is generally normal.• Dyspnea may be caused by
Pleural effusion Impaired respiratory muscle function Diminished ventilatory drive Sleep apnea
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Gastro-intestinal Tract
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• Gastro-intestine Constipation, fecal impaction (myxedema
megacolon). Ileus, Decreased GI motility, Gaseous distention Ascites Achlorhydria Elevations in the serum levels of CEA Malabsorption
• Hepatic Increased LDL / TC Elevated LDL + triglycerides Levels of aminotransaminases may be elevated The gallbladder contracts sluggishly and may be
distended
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51
Genito-Urinary system
51Dr. MVasheghani
• Renal
• Fluid retention and oedema
• Decreased GFR
• Reproductive system
• Infertility, ↑ Miscarriage
• Menometrorrhagia, oligomenorrhea or amenorrhea
• Impotence, ↑ Prolactin
• ↓ Libido both sexes
• Premature ovarian failure
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52
Musculoskeletal
52Dr. MVasheghani
• Muscle stiffness, cramps, pain, weakness, myalgia
• Slow muscle-stretch reflexes, muscle enlargement, atrophy
• Carpel tunnel syndrome• arthralgias• Pseudomyotonia
• Slow relaxation of DTR
• Arthralgias,
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53
Central Nervous System
53Dr. MVasheghani
• Memory and concentration impairment• Depression with limited initiative and sociability.• Cognitive deficits can range from mild lapses in
memory to delirium, dementia, seizures, psychosis, and myxedema coma
• Cerebellar ataxia, myotonia, paresthesias• Hashimoto’s encephalopathy has been defined as a
steroid-responsive syndrome associated with TPO antibodies, myoclonus, and slow-wave activity on electroencephalography
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54
Clinical Signs of Hypothyroidism
•Coarse Hair; Diffuse thinning of scalp hair •The skin may be coarse, dry, pale or yellow and cool due to peripheral vasoconstriction; Brritle nails
•Thinning of lateral 1/3 of eye brows (Queen Anne sign)
•Puffiness of eyes and face
Goiter (not in all cases), the thyroid gland may be normal in size, diffusely enlarged, or atrophic, It may be soft and smooth with a lobular texture, or firm and irregular with a variegated nodular texture ; cervical incisional scars •Low hoarse speech and slow movements; slow and dysarthric speech•Bradycardia, pericardial effusion, diastolic hypertension, Non-pitting edema (myxoedema), ↓ heart sound•Delayed relaxation of DTR with a marked delay in the terminal relaxation phase (Hang up reflex)
54Dr. MVasheghani
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Abnormal laboratory in hypothyroidism• Anemia (25-50% of patients)• Hyponautremia• Hypercholesterolemia (90% of patients)
14% of patients hypercholesterolemia have hypothyroidism
• Abnormal LFT• Elevated CPK and LDH• Hyperprolactinemia• Decreased GH secretion and action• Schmidt syndrome (Primary adrenocortical insufficiency)
Dr. MVasheghani55
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5656Dr. MVasheghani
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5757Dr. MVasheghani
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58
Clinical features
58Dr. MVasheghani
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5959Dr. MVasheghani
Pretibial Myxedema Myxedema with Carotinemia
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Pituitary Tumor – Secondary Hypo
Normal Pituitary Fossa
Dr. MVasheghani
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Massive Pericardial Effusion
61
Feb1998
Dr. MVasheghani
Sep 1998 Dec1999
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6262Dr. MVasheghani
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63
Before Therapy After Therapy
Dr. MVasheghani63
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6464Dr. MVasheghani
Before Therapy After Therapy
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65
Hypothyroidism and DepressionHave Many Common Features
Depression
• Sleep decrease• Suicidal ideation
• Weight loss• Appetite increase/
decrease
Nemeroff CB, J Clin Psychiatry. 1989;50(suppl):13-20.
• Bradycardia• Cardiac and lipid
abnormalities• Cold intolerance• Delayed reflexes
• Goiter• Hair and skin
changes
• Constipation• Appetite decrease
• Decreased concentration• Decreased libido
• Delusions• Depressed mood
• Diminished interest• Sleep increase
• Weight increase• Fatigue
Hypothyroidism
Dr. MVasheghani65
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6666Dr. MVasheghani
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67
Classification
67Dr. MVasheghani
• Established reference ranges for TSH levels is 0.5 to 4.5 mIU/L.
• A low free T4 level with a persistently elevated TSH level represents overt primary hypothyroidism.
• A low-normal free T4 level with an elevated TSH level is termed mild or subclinical primary hypothyroidism.
• Other uncommon causes of isolated TSH elevation include: Recovery from severe systemic illnessRenal failureAdrenal insufficiency.
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68
TFT ASSESSMENT
68Dr. MVasheghani
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Condition that affect TSH level
Low serum TSH
Dr. MVasheghani
Primary hyperthyroidismIncomplete recovery of hyperthyroidismNTIHigh level of hCG, early pregnancy, molar pregnancy, coriocarcinomaDrugs: dopamine agonist, GC, somatostatin analogsCentral hypothyroidism
Primary hypothyroidism Recovery from NTI Drugs: dopamine antagonist,
amiodarone, OCG dye TSH-producing pituitary
adenoma Adrenal insufficiency Heterophilic antibody
interference Generalized thyroid hormone
resistant
High serum TSH
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• The underlying cause of primary hypothyroidism is usually clinically
obvious, and laboratory testing is unnecessary in most cases.
• When confirmation is required (e.g., to convince a patient the
condition is permanent), serum antithyroid antibodies may be
assessed. Measurement of Anti-TPO Ab is a more sensitive test
than Anti-Tg Ab for this purpose.
• However, 10% of patients with histologically documented
autoimmune thyroiditis have no circulating antithyroid antibodies.
70Dr. MVasheghani
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• When clinical findings suggest the possibility of secondary hypothyroidism such as: The presence of a sellar massPrevious pituitary surgery or irradiationOther pituitary axis hormone deficiencies
• The serum TSH and free T4 level must be assessed. • In these settings, a low or even low-normal free T4 level
can confirm the diagnosis. • The TSH level in patients with secondary hypothyroidism
can be low, normal, or even modestly elevated.
Dr. MVasheghani
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Diagnosis
72Dr. MVasheghani
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Treatment
73Dr. MVasheghani
•The goals of thyroid hormone replacement therapy are: To replace endogenous thyroid hormone productionTo avoid iatrogenic thyrotoxicosisTo treat systemic complications of severe hypothyroidism, rarely.
•Therapy with levothyroxine sodium products requires individualized patient dosing:
Careful titration: use a formulation with consistent dosesClinical evaluation: symptoms resolve more slowly than TSH responseLaboratory monitoring: need consistent, sensitive TSH measurements
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Treatment
74Dr. MVasheghani
• Treatment depends upon :
Cause and severity of disease
Patients age and weight
Goiter size
Comorbid states and treatment
Cardiovascular health
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• LT4, LT3 or LT4+LT3
• LT4 therapy Choice
• LT4+LT3 therapy Sometimes
• Is there any place for liothyronine
alone as long-term replacement?
75
NO ‼
Dr. MVasheghani
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7676Dr. MVasheghani
1.6 micg/kg BW, at least 30 min before breakfast.
The goal of treatment being a normal TSH, ideally in the lower half of the reference range.
TSH should be measured 4 - 8 week later.
Once an adequate dose has been established, the TSH level should be checked annually.
In patients with secondary hypothyroidism, the serum free T4 level should be monitored 2 to 4 weeks after the thyroxine dose is started or adjusted, with a target free T4 level in the upper half of the reference range.
Clinical Hypothyroidism
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Thyroid hormone replacement
• Levothyroxine sodium is choice.
• It is well absorbed and 7 day half-life.
• Thyroxine is physiologically deiodinated to the more biologically active T3 in peripheral tissues.
• Thyroxine has a narrow therapeutic index, and doses differing by as little as 12% can have clinicalconsequences.
• Bioavailability may differ by as much as 12% among different preparations. Consequently, adherence to a single thyroxine formulation is advisable.
77Dr. MVasheghani
2004 AACE, TES, and ATA Joint Position Statement on the Use and Interchangeability ofThyroxine Products
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7878
Primary Hypothyroidism Rx. Algorithm
TSH >3.0 IU/mL TSH <0.5 IU/mL
Initial Levothyroxine Dose
IncreaseLevothyroxine
Dose by12.5 to 25 g/d
Repeat TSH Test
6-8 Weeks
TSH 0.5- 2.0 IU/mLSymptoms Resolved
Measure TSH at 6 Months, Then Annually or
When Symptomatic
Continue Dose DecreaseLevothyroxine
Dose by12.5 to 25 g/d
Singer PA, et al. JAMA. 1995;273:808-812. Demers LM, Spencer CA, eds. The National Academy of
Clinical Biochemistry Web site. Available at: http://www.nacb.org/lmpg/thyroid_lmpg.stm. Accessed
July 1, 2003.Dr. MVasheghani
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CONT…
• In patients of normal body weight who are taking 200 g of levothyroxine per day, an elevated TSH level :Poor adherence to treatment.Malabsorption (e.g., celiac disease, small-bowel surgery)Drug:
• Estrogen or selective estrogen receptor modulator therapy, Lovastatin, Amiodarone. PPI, TK inhibitors
Thyroxine doses should be separated from these substances by 8 hours or longer
Ingestion with a meal
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Interfrence with LT4 replacement
80Dr. MVasheghani
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• The clinical effects of levothyroxine replacement are slow to appear. Patients may not experience full relief from symptoms until 3–6 months after normal TSH levels are restored.
• patients who miss a dose can be advised to take two doses of the skipped tablets at once.
81Dr. MVasheghani
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What is a Normal TSH?• In their 2002 position statement, AACE used an
upper limit of normal for TSH of 3.0mIU/L established in a population of patients carefully screened for thyroid disease by the National Academy of Biochemistry in 2002.
• However, in 2004 a statement was published in JAMA maintaining that the upper limit of TSH should remain at 4.5 mIU/L, rather than 3.0-3.5 as some other organizations have suggested.
82
AACE MEDICAL GUIDELINES FOR CLINICAL PRACTICE FOR THE EVALUATION AND TREATMENT OF HYPERTHYROIDISM AND HYPOTHYROIDISM. ENDOCRINE PRACTICE Vol 8 No. 6 2002JAMA 2004; 291:228-238
Dr. MVasheghani
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Complications Pseudotumor cerebri in children
• Idiosyncratic and occurs months after treatment has begun.
Thyrotoxicosis usually accompany significant degrees of overtreatment
Bone mineral loss, especially in postmenopausal women
Increase the risk of AF in older individuals, even a modestly excessive thyroxine
dose
Exacerbate myocardial ischemia in patients with underlying CAD
Coexisting adrenal insufficiency may be unmasked.
Transient hair loss
Acute sympathomimetic symptoms
83Dr. MVasheghani
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Subclinical Hypothyroidism
• Subclinical hypothyroidism refers to biochemical evidence of thyroid hormone deficiency .
• An isolated elevated TSH level with normal T3 and T4 levels • It is important to confirm that any elevation of TSH is
sustained over a 3-month period before treatment is given.• There are no universally accepted recommendations for the
management of subclinical hypothyroidism.• Treatment is administered by starting with a low dose of
levothyroxine (25–50 μg/d) with the goal of normalizing TSH.
84Dr. MVasheghani
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Subclinical Hypothyroidism
• Who should be treated? Patient is symptomatic
TSH levels >=10 mU/L.
TPO antibodies positive
Woman who wishes to conceive or is pregnant
Any evidence of heart disease
• Maintain TSH in normal range• In patients not receiving Levothyroxine therapy,
check TSH every 3-6 months(annually) or when symptoms occur
85Dr. MVasheghani
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Special Treatment Considerations• Women should ensure that they are euthyroid prior to
conception and during early pregnancy.
• The dose of levothyroxine may need to be increased:
↑ dose 50%(25-75%) during pregnancy
Post-surgical or post-Iodine ablation
Nephrotic syndrome due to rapid clearance of thyroid hormone
• The dose of levothyroxine may need to be decreased:
↓ Dose 20% in elderly patients
Adults with known or suspected ischemic heart disease
86Dr. MVasheghani
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Hypothyroidism & Pregnancy
• Fetal neural development delay or preterm delivery. • The presence of thyroid autoantibodies alone, in a euthyroid pt,
is associated with miscarriage and preterm delivery.• TFT should be evaluated immediately and every 4 w during the
first half of the pregnancy, then every 6–8 w depending on whether LT4 dose adjustment is ongoing after 20 W gestation.
• The goal TSH of less than 2.5 mIU/L during the first trimester and less than 3.0 mIU/L during the second and third trimesters.
• After delivery, LT4 doses return to pre-pregnancy levels. • Pregnant women should be separate ingestion of prenatal
vitamins and iron supplements from LT4 by at least 4 h.
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Hypothyroidism & Heart Disease
• Elderly patients may require 20% less thyroxine than younger patients.
• The starting dose of levothyroxine is 12.5–25 μg/d with similar increments every 2–3 months until TSH is normalized.
• In some patients, it may be impossible to achieve full replacement despite optimal antianginal treatment.
88Dr. MVasheghani
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Hypothyroidism & Surgery• Emergency surgery is generally safe in
patients with untreated hypothyroidism.
• Elective or routine surgery in a hypothyroid patient should be deferred until euthyroidism is achieved.
89Dr. MVasheghani
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Hypothyroidism Following Hemithyroidectomy
• The incidence & risk factors for hypothyroidism in patients undergoing partial thyroid surgery remains unclear. With reported incidence of b/w 6.5% & 45% and up to 65% in patient with head and neck ca .
• Risk factors are the presence of :Anti-TPO antibody Thyroiditis in pathologyMultinodular goiterPreoperative thyrotoxicosisThyroid remnant < 6 gElderly patients
90Dr. MVasheghani
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91DAMAVAND MOUNTAIN
TEHRAN , IRAN