Thyroid Flashcards

Question

Toxic adenoma Radioisotope Thyroid Scan

Answer 1

single intense area of uptake with suppression elsewhere

Answer 2

clinical, physiological, and biochemical findings in response to elevated thyroid hormone

Answer 3

``` Tremor Heart rate up/afib/palpitations Yawning (fatigued) Restlessness Oligomenorrhea/amenorrhea/decreased fertility Intolerance to heat Diarrhea Irritability Sweating/warm skin Muscle wasting (proximal)/weight loss with increased appetite and thirst ``` ``` Other: Hypokalemic periodic paralysis (more common in Asians) Fine hair Vitiligo Soft nails with onycholysis (Plummer's nails) Palmar erythema Pruritis Decreased bone mass ``` Graves' disease - clubbing (acropachy) and pretibial myxedema (rare) Leeukopenia, lymphocytosis, splenomegaly, lymphadenopathy Lid lag, retraction, proptosis, diplopia, decreased acuity, uffiness, conjunctival injection

Answer 4

TSH dec Free T3/T4 inc Thyroid antibodies up to 50% of cases RAIU decreased (increases once entering hypothyroid phase, when TSH rises) In classical subacute painful thyroiditis, ESR increased Can be subacute, silent or postpartum

Answer 5

Graves' Disease Toxic Nodular Goitre Toxic Nodule Thyroiditis

Answer 6

Hashimoto's Congenital Iatrogenic (thionamides, radioactive iodine or surgery) Hypothyroid phase of thyroiditis

Answer 7

Pituitary thyrotrophoma Pituitary thyroid hormone receptor resistance Increased hCG (ex. pregnancy)

Answer 8

* thionamides: propylthiouracil (PTU) or methimazole (MMI); MMI recommended (except in first trimester pregnancy) * β-blockers for symptom control * radioactive iodine thyroid ablation for Graves’ disease * surgery in the form of hemi, subtotal, or complete thyroidectomy

Answer 9

an autoimmune disorder characterized by autoantibodies to the TSH receptor that leads to hyperthyroidism

Answer 10

* occurs at any age with peak in 3rd and 4th decade * F:M = 7:1, 1.5-2% of U.S. women * familial predisposition: 15% of patients have a close family member with Graves’ disease and 50% have family members with positive circulating antibodies * association with HLA B8 and DR3 * may be associated with other inherited autoimmune disorders (e.g. pernicious anemia, Hashimoto’s disease)

Answer 11

Graves' Disease

Answer 12

* autoimmune disorder due to a defect in T-suppressor cells * B lymphocytes produce TSI that binds and stimulates the TSH receptor and stimulates the thyroid gland * immune response can be triggered by postpartum state, iodine excess, lithium therapy, viral or bacterial infections, glucocorticoid withdrawal * ophthalmopathy (thyroid associated orbitopathy) is a result of increased tissue volume due to inflammation and accumulation of glycosaminoglycans, stimulated by TSI, that increase osmotic pressure within the orbit; this leads to fluid accumulation and displacement of the eyeball forward * dermopathy may be related to cutaneous glycosaminoglycan deposition

Answer 13

* signs and symptoms of thyrotoxicosis * diffuse thyroid goitre ± thyroid bruit secondary to increased blood flow through the gland • ophthalmopathy: NO SPECS (in order of changes usually) No signs Only signs: lid lag, lid retraction Soft tissue: periorbital puffiness, conjuctival injection, chemosis Proptosis/exophthalmos Extraocular (diplopia) Corneal abrasions (since unable to close eyes) Sight loss (plus signs of hyperthyroidism: lid retraction, characteristic stare) * dermopathy (rare): pretibial myxedema (thickening of dermis that manifests as non-pitting edema * acropachy: clubbing and thickening of distal phalanges

Answer 14

* low TSH * increased free T4 (and/or increased T3) * positive for TSI (specific but not sensitive for Graves’ disease) * increased radioactive iodine (I 131) uptake * homogeneous uptake on thyroid scan (only do this test in the presence of nodule)

Answer 15

• thionamides: propylthiouracil (PTU) or methimazole (MMI) ■ iodinated contrast agents: sodium ipodate and iopanoic acid can inhibit conversion of T4 to T3 and are especially effective in combination with MMI ■ MMI preferred vs. PTU due to longer duration of action (once daily for most), more rapid efficacy, and lower incidence of side effects ■ in pregnancy: use PTU during first trimester and MMI during second and third trimester. MMI is contraindicated in the first trimester due to risk of aplasia cutis; MMI is preferred in the second and third trimester due to the potential risk of hepatotoxicity with PTU in the second and third trimesters • symptomatic treatment with β-blockers • thyroid ablation with radioactive 131I if PTU or MMI trial does not produce disease remission ■ high incidence of hypothyroidism after 131I requiring lifelong thyroid hormone replacement ■ conraindicated in pregnancy ■ may worsen ophthalmopathy • subtotal or total thyroidectomy (indicated for large goitres, suspicious nodule for Ca, if patient is intolerant to thionamides and refusing RAI ablation) ■ risks include hypoparathyroidism and vocal cord palsy ``` • ophthalmopathy/orbitopathy ■ smoking cessation is important ■ prevent drying of eyes ■ high dose prednisone in severe cases ■ orbital radiation, surgical decompression ``` Glucocorticoids have been useful in the treatment of severe Graves’ hyperthyroidism and thy oid storm, by inhibiting the conversion of peripheral T4 to T3 Lithium is also used to treat Graves’ hyperthyroidism. It acts by blocking thyroid hormone release, but its toxicity has limited its use in practice

Answer 16

* course involves remission and exacerbation unless gland is destroyed by radioactive iodine or surgery * lifetime follow-up needed * risk of relapse is 37%, 21%, 6% in thionamides, radioiodine ablation, and surgery groups, respectively

Answer 17

■ PTU and MMI inhibit thyroid hormone synthesis by inhibiting peroxidase-catalyzed reactions, thereby inhibiting organification of iodide, blocking the coupling of iodotyrosines ■ PTU also inhibits peripheral deiodination of T4 to T3 ■ continue treatment until remission occurs (20-40% of patients achieve spontaneous remission at 6-18 mo of treatment) ■ small goitre and recent onset are good indicators for long-term remission with medical therapy ■ major side effects: hepatitis, agranulocytosis, and fever/arthralgias ■ minor side effects: rash

Answer 18

acute inflammatory disorder of the thyroid gland characterized by an initial thyrotoxic state followed by hypothyroidism eventually followed by euthyroidism in most cases • two subtypes: painful (“De Quervain’s”) and painless (“Silent”)

Answer 19

* acute inflammation of the thyroid gland characterized by giant cells and lymphocytes * disruption of thyroid follicles by inflammatory process results in the release of stored hormone rather than excessive production of new thyroid hormone * painful = viral (usually preceded by URTI), De Quervain’s (granulomatous thyroiditis) • painless = postpartum, auto-immune, lymphocytic ■ occurs in 5-10% of postpartum mothers and is symptomatic in 1/3 of patients

Answer 20

* painful (thyroid, ears, jaw, and occiput) or painless * fever and malaise may be present, especially in De Quervain’s * postparum: thyrotoxicosis 2-3 mo postpartum with a subsequent hypothyroid phase at 4-8 mo pospartum * may be mistakenly diagnosed as postpartum depression

Answer 21

* initial elevated free T4, T3, low TSH, RAIU markedly reduced * marked elevation of ESR in painful variety only * as disease progresses values consistent with hypothyroidism may appear

Answer 22

* painful – high dose NSAIDs prednisone may be required for severe pain, fever, or malaise * iodinated contrast agents (eg. iopanoic acid, ipodate) to inhibit peripheral conversion of T4 to T3 * β-adrenergic blockade is usually effective in reversing most of the hypermetabolic and cardiac symptoms in both subtypes * if symptomatically hypothyroid, may treat short-term with thyroxine

Answer 23

* full recovery in most cases, but permanent hypothyroidism in 10% of painless thyroiditis * postpartum: most resolve spontaneously without need for supplementation, however may recur with subsequent pregnancies

Answer 24

RAI therapy for GD is associated with a small but definite increased risk of development or worsening of Graves' ophthalmopathy (GO) compared with antithyroid drugs. Steroid prophylaxis is beneficial for patients with preexisting GO.

Answer 25

* autonomous thyroid hormone production from a functioning adenoma that is hypersecreting T3 and T4 * may be singular (toxic adenoma) or multiple (toxic multinodular goitre [Plummer’s disease])

Answer 26

* goitre with adenomatous changes * tachycardia, heart failure, arrhythmia, weight loss, nervousness, weakness, tremor, and sweats * seen most frequently in elderly people, often with presentation of atrial fibrillation

Answer 27

* low TSH, high T3 and T4 | * thyroid scan with increased RAIU in nodule(s) and suppression of the remainder of the gland

Answer 28

* initiate therapy with PTU or MMI to attain euthyroid state * use high dose radioactive iodine (I-131) to ablate hyperfunctioning nodules * β-blockers often necessary for symptomatic treatment prior to definitive therapy * surgical excision may also be used as 1st line treatment

Answer 29

* acute exacerbation of all of the symptoms of thyrotoxicosis presenting in a life-threatening state secondary to uncontrolled hyperthyroidism – medical emergency! * rare, but serious with mortality rate between 10-30%

Answer 30

• often precipitated by infection, trauma, or surgery in a hyperthyroid patient

Answer 31

• sepsis, pheochromocytoma, malignant hyperthermia, drug overdose, neuroleptic malignant syndrome

Answer 32

* hyperthy oidism * extreme hyperthermia (≥40°C), tachycardia, vomiting diarrhea, vascular collapse, hepatic failure with jaundice, and confusion * tachyarrhythmia, CHF, shock * mental status changes ranging from delirium to coma

Answer 33

* increased free T3 and T4, undetectable TSH | * ± anemia, leukocytosis, hyperglycemia, hypercalcemia, elevated LFTs

Answer 34

* fluids, electrolytes, and vasopressor agents should be used as indicated * a cooling blanket and acetaminophen can be used to treat the pyrexia * propranolol or other β blockers that additionally decrease peripheral conversion of T3 → T4 can be used, but should be used with caution in CHF patients as it may worsen condition * PTU is the anti-thyroid drug of choice and is used in high doses • give iodide, which acutely inhibits the release of thyroid hormone, one hour after the first dose of PTU is given ■ Sodium iodide 1 g IV drip over 12h q12h OR ■ Lugol’s solution 2-3 drops q8h OR ■ Potassium iodide (SSKI) 5 drops q8h • dexamethasone 2-4 mg IV q6h for the first 24-48 hours lowers body temperature and inhibits peripheral conversion of T3 → T4

Answer 35

• probably <20% mortality rate if rapidly recognized and treated

Answer 36

• clinical syndrome caused by cellular responses to insufficient thyroid hormone production

Answer 37

* 2-3% of general population * F:M = 10:1 * 10-20% of women over age 50 have subclinical hypothyroidism (normal T4, TSH mildly elevated) * iodine deficiency most common cause worldwide, but not in North America

Answer 38

• primary hypothyroidism (90%) ■ inadequate thyroid hormone production secondary to intrinsic thyroid defect ■ iatrogenic: post-ablative (I-131 or surgical thyroidectomy) ■ autoimmune: Hashimoto’s thyroiditis, chronic thyroiditis, idiopathic, burnt out Graves’ ■ hypothyroid phase of subacute thyroiditis ■ drugs: goitrogens (iodine), PTU, MMI, lithium ■ infiltrative disease (progressive systemic sclerosis, amyloid) ■ iodine deficiency ■ congenital (1/4,000 births) ■ neoplasia secondary hypothyroidism: pituitary hypothyroidism ■ insufficiency of pituitary TSH • tertiary hypothyroidism: hypothalamic hypothyroidism ■ decreased TRH from hypothalamus (rare) • peripheral tissue resistance to thyroid hormone (Refetoff syndrome)

Answer 39

In current RCTs, levothyroxine replacement therapy for subclinical hypothyroidism did not result in improved survival or decreased cardiovascular morbidity. Data on health-related quality of life and symptoms did not demonstrate significant differences between intervention groups. Some evidence indicates that levothyroxine replacement improves some parameters of lipid profiles and left ventricular function.

Answer 40

overt primary hypothyroidism Serum TSH - inc Free T4 - dec subclinical primary hypothyroidism Serum TSH - inc Free T4 - normal secondary hypothyroidism Serum TSH - dec or not appropriately elevated Free T4 - dec

Answer 41

General - Fatigue, cold intolerance, slowing of mental and physical performance, hoarseness, macroglossia CVS - Pericardial effusion, bradycardia, hypotension, worsening CHF + angina, hypercholesterolemia, hyperhomocysteinemia, myxedema heart Respiratory - Decreased exercise capacity, hypoventilation secondary to weak muscles, decreased pulmonary responses to hypoxia, sleep apnea due to macroglossia GI - Weight gain despite poor appetite, constipation Neurology - Paresthesia, slow speech, muscle cramps, delay in relaxation phase of deep tendon reflexes (“hung reflexes”), carpal tunnel syndrome, asymptomatic increase in CK, seizures GU - Menorrhagia, amenorrhea, impotence Dermatology - Puffiness of face, periorbital edema, cool and pale, dry and rough skin, hair dry and coarse, eyebrows thinned (lateral 1/3), discolouration (carotenemia) Hematology - Anemia: 10% pernicious due to presence of anti-parietal cell antibodies with Hashimoto’s thyroiditis ``` HIS FIRM CAP Hypoventilation Intolerance to cold Slow HR Fatigue Impotence Renal impairment Menorrhagia/amenorrhea Constipation Anemia Paresthesia ```

Answer 42

* L-thyroxine (dose range: 0.05-0.2 mg PO OD ~1.6 µg/kg/d) * elderly patients and those with CAD: start at 0.025 mg daily and increase gradually every 6 wk (start low, go slow) * after initiating L-thyroxine, TSH needs to be evaluated in 6 wk; dose is adjusted until TSH returns to normal reference range * once maintenance dose achieved, follow-up TSH with patient annually • secondary/tertiary hypothyroidism ■ monitor via measurement of free T4 (TSH is unreliable in this setting)

Answer 43

Hashimoto's Thyroiditis

Answer 44

• chronic autoimmune thyroiditis characterized by both cellular and humoral factors in the destruction of thyroid tissue • two major forms: goitrous and atrophic; both forms share same pathophysiology but differ in the extent of lymphocytic infiltration, fibrosis, and thyroid follicular cell hyperplasia goitrous variant usually presents with a rubbery goitre and euthyroidism, then hypothyroidism becomes evident ■ associated with fibrosis • atrophic variant patients are hypothyroid from the start ■ associated with thyroid lymphoma

Answer 45

* defect in clone of T-suppressors leads to cell-mediated destruction of thyroid follicles * B lymphocytes produce antibodies against thyroid components including thyroglobulin, thyroid peroxidase, TSH receptor, Na+/I– symporter

Answer 46

* female gender (F:M = 7:1) * genetic susceptibility: increased frequency in patients with Down’s syndrome, Turner’s syndrome, certain HLA alleles, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) * family Hx or personal Hx of other autoimmune diseases * cigarette smoking * high iodine intake * stress and infection

Answer 47

* high TSH, low T4 (not necessary to measure T3 as it will be low as well) * presence of anti-thyroid peroxidase (TPOAb) and thyroglobulin antibodies (TgAb) in serum

Answer 48

• if hypothyroid, replace with L-thyroxine (analog of T4)

Answer 49

• if hypothyroid, replace with L-thyroxine (analog of T4)

Answer 50

* severe hypothyroidism complicated by trauma, sepsis, cold exposure, MI, inadvertent administration of hypnotics or narcotics, and other stressful events – medical emergency! * rare high level of mortality when it occurs (up to 40%, despite therapy)

Answer 51

• hallmark symptoms of decreased mental status and hypothermia; hyponatremia, hypotension, hypoglycemia, bradycardia, hypoventilation, and generalized edema often present

Answer 52

* decreased T4, increased TSH, decreased glucose | * check ACTH and cortisol for evidence of adrenal insufficiency

Answer 53

* aggressive treatment required * ABCs: ICU admission * corticosteroids (for risk of concomitant adrenal insufficiency): hydrocortisone 100 mg q8h * L-thyroxine 02-0.5 mg IV loading dose, then 0.1 mg IV OD until oral therapy tolerated; also consider T3 therapy * supportive measures: mechanical ventilation, vasopressor drugs, passive rewarming, IV dextrose, fluids if necessary (risk of overload) * monitor for arrhythmia

Answer 54

* changes in circulating thyroid hormones amongst patients with serious illness, trauma, or stress * not due to intrinsic thyroid or pituitary disease * initially low free T3 may be followed by low TSH and if severe illness low free T4 * with recovery of illness, TSH may overshoot and become transiently high

Answer 55

• abnormalities include alterations in ■ peripheral transport and metabolism of thyroid hormone ■ regulation of TSH secretion ■ thyroid function itself • may be protective during illness by reducing tissue catabolism

Answer 56

• initially decreased free T3 followed by decreased TSH and finally decreased free T4

Answer 57

* treat the underlying disease; thyroid hormone replacement worsens outcomes * thyroid function tests normalize once patient is well (initially with a transient increase in TSH)

Answer 58

• generalized enlargement of the thyroid gland in a euthyroid individual that does not result from inflammatory or neoplastic processes

Answer 59

• the appearance of a goitre is more likely during adolescence, pregnancy, and lactation because of increased thyroid hormone requirements ■ early stages goitre is usually diffuse ■ later stages: multinodular non-toxic goitre with nodule, cyst formation and areas of ischemia, hemorrhage, and fibrosis

Answer 60

* iodine deficiency or excess * goitrogens: brassica vegetables (e.g. turnip, cassava) * drugs: iodine, lithium, para-aminosalicylic acid * any disorder of hormone synthesis with compensatory growth * peripheral resistance to thyroid hormone

Answer 61

* remove goitrogens * radioiodine therapy (need very high doses given low iodine uptake, used as last resort) * suppression with L-thyroxine (rarely done) * surgery may be necessary for severe compressive symptoms

Answer 62

* compression of neck structures causing stridor, dysphagia, pain, and hoarseness * multinodular goitre may become autonomous leading to toxic multinodular goitre and hyperthyroidism

Answer 63

* clearly defined discrete mass, separated from the thyroid parenchyma * palpable nodules are found in approximately 5% of women and 1% of men

Answer 64

* benign tumours (e.g. colloid nodule, follicular adenoma) * thyroid malignancy * hyperplastic area in a multinodular goitre * cyst: true thyroid cyst, area of cystic degeneration in a multinodular goitre

Answer 65

sTSH 1. If low TSH - thyroid scan a) It hot nodule - no biopsy, treat hyperthyroidism b) If cold nodule - thyroid ultrasound and biopsy, treat hyperthyroidism 2. Normal/elevated TSH - Thyroid ultrasound and biopsy