hypothyroidism Flashcards

1
Q

hypothyroidism

A

-Iodine deficiency
-Rare in the US
-Remains the MC cause of hypothyroidism worldwide
-In areas of iodine sufficiency
-Autoimmune disease (Hashimoto’s thyroiditis)
-Iatrogenic causes (treatment of hyperthyroidism) are also very common

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2
Q

epidemiology

A

-Neonatal/congenital hypothyroidism - more often in Caucasian than in African-American infants
-Spontaneous hypothyroidism - European Caucasians > African-Americans
-Genetics- Thyroid development defects are sometimes congenital
-Geography
-Incidence is 10x higher than average in iodine-deficient areas
-Also increased in areas exposed to waterborne goitrogens or where there is excessive consumption of goitrogens (e.g. cassava)
-Incidence is raised in areas exposed to excessive radiation
-More in Japanese – high iodine content & genetic factors

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3
Q

etiology- primary

A

-Autoimmune hypothyroidism: Hashimoto’s thyroiditis, atrophic thyroiditis -> Hepatitis C and Interferon can put at increased risk
-Iatrogenic: 131I treatment, subtotal or total thyroidectomy, external irradiation of neck for lymphoma or cancer
-Drugs: iodine excess (including iodine-containing contrast media and amiodarone), lithium, antithyroid drugs,
-Congenital hypothyroidism: absent or ectopic thyroid gland, dyshormonogenesis, TSH-R mutation
-Iodine deficiency
-Infiltrative disorders: amyloidosis, sarcoidosis, hemochromatosis etc.
-Overexpression of type 3 deoiodinase in infantile hemangioma
-After 131-I treatment or subtotal thyroidectomy for Graves’ disease

-Transient:
-asymptomatic - deont need to treat
-Silent thyroiditis, including postpartum thyroiditis
-Subacute thyroiditis
-Withdrawal of T4 treatment in pts. with an intact thyroid

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4
Q

etiology: secondary

A

-Hypopituitarism: tumors, pituitary surgery or irradiation, infiltrative disorders, Sheehan’s syndrome, trauma, genetic forms of combined pituitary hormone deficiencies
-Isolated TSH deficiency or inactivity - rare
-Bexarotene treatment – anti-neoplastic agent
-Hypothalamic disease: tumors, trauma, infiltrative disorders, idiopathic
-TSH levels may be LOW, normal, or even slightly increased in secondary hypothyroidism
-Treatment - maintain unbound T4 levels in the upper half of the reference range, as TSH levels cannot be used to monitor therapy
-Diagnosed in the context of other anterior pituitary hormone deficiencies -> Isolated TSH deficiency is very rare
-Hypothyroidism - due to secretion of immunoactive but bio-inactive forms of TSH

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5
Q

mild thyroid failure

A

-May be present in cases of:
-Gastrointestinal disease
-Hyperlipidemia
-Coronary artery disease
-Hypertension

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6
Q

iatrogenic hypothyroidism

A

-Commonest cause of hypothyroidism
-Can often be detected by screening before symptoms develop
-In the first 3 to 4 months after radioiodine treatment, transient hypothyroidism may occur due to reversible radiation damage rather than to cellular destruction
-Low-dose thyroxine treatment can be withdrawn if recovery occurs

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7
Q

chronic iodine excess

A

-Paradoxically, chronic iodine excess can also induce goiter and hypothyroidism (normally hyper with high iodine)
-Intracellular events - for this effect are unclear
-Individuals with autoimmune thyroiditis are especially susceptible
-Iodine excess responsible for hypothyroidism in up to 13% of patients treated with amiodarone
-Other drugs, particularly lithium, may also cause hypothyroidism

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8
Q

predisposing factors

A

-More prevalent with increasing age; More prevalent in women
-Autoimmune diseases
-Incidence- 5-10/1000 in general population.
-Prevalence- Prevalence is 50-100/1000 in general population.
-Frequency- Neonatal/congenital hypothyroidism is seen in 0.25/1000 live births

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9
Q

associated autoimmune diseases

A

-Hypoparathyroidism
-Diabetes Mellitus 1
-Pernicious anemia
-SLE
-Rheumatoid arthritis
-Sjogren’s Syndrome
-Addison’s disease*- must watch bc if you dont give cortisol they will die
-Vitiligo
-Myasthenia gravis

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10
Q

symptoms

A

-Tiredness, weakness
-Dry skin
-Feeling cold
-Hair loss
-Constipation
-Weight gain with poor appetite
-Dyspnea
-Hoarse voice
-Menorrhagia (later oligomenorrhea or amenorrhea)
-Paresthesia
-Impaired hearing
-Difficulty concentrating and poor memory

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11
Q

signs

A

-Dry coarse skin; cool peripheral extremities
-Puffy face, hands- Myxedema -> Non pitting edema! (pre-tibial is hyperthyroid)
-Lower extremities – pitting edema
-Diffuse alopecia
-Bradycardia
-Peripheral edema
-Delayed tendon reflex relaxation
-Carpal tunnel syndrome
-Serous cavity effusions

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12
Q

subclinical hypothyroidism

A

-May be asymptomatic or manifest as:
-Depression
-Cognitive problems
-Weight gain
-Fatigue
-Irregular menstruation
-Infertility

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13
Q

other clinical manifestations

A

-Insidious onset
-Patient may become aware of symptoms only when euthyroidism is restored
-Hashimoto’s thyroiditis - present with a goiter rather than symptoms of hypothyroidism
-Goiter may not be large
-Usually irregular and firm
-Often possible to palpate a pyramidal lobe (middle part- might be remnant of thyroglossal duct cyst) -> Vestigial remnant of the Thyroglossal duct

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14
Q

diff dx

A

-Aging
-Congestive heart failure
-Depression
-Accidental hypothermia
-Sick Euthyroid syndrome
-Chronic renal failure
-Down’s Syndrome
-Nephrotic syndrome
-Amyloidosis
-Drug intoxication

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15
Q

evaluation

A

-High TSH, low T4
-TSH assay and free T4 levels confirm diagnosis -> Free T3 levels - may or may not be useful
-Patients with primary (but not supra-thyroid) clinical or subclinical hypothyroidism have raised TSH levels
-Patients with clinical, overt hypothyroidism have decreased free T4 levels, but only 1/3 of such patients have decreased free T3 levels
-Those with subclinical hypothyroidism can have normal T4 and/or T3 levels
-Serum lipid levels - to detect any dyslipidemia
-CBC - to detect any anemia

-TSH - primary test in diagnosis of hypothyroidism
-Serum levels are raised if the patient has overt or mild primary hypothyroidism but may be normal or low in suprathyroid hypothyroidism
-Free T4 assay: clinical, overt hypothyroid patients have reduced free T4 levels;
-Free T3 assay: only one third of clinical, overt hypothyroid patients have reduced free T3 levels;

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16
Q

thyroid autoantibody

A

-Thyroid autoantibody (also for graves)
May be performed
-Positive result - in 95% of patients with autoimmune thyroiditis
-Not often employed in clinical decision-making though some use this test to decide whether to treat cases of mild thyroid failure
-May be confirmatory in patients with thyroid tenderness

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17
Q

treatment

A

-Levothyroxine (T4)
-stick with same supplier for greatest efficacy -> dont switch to synthyroid
-Only recommended treatment
-Usually started at a dose between 25-75mcg, and titrated to target
-Takes 4-6 weeks for TSH blood level to adjust after a change in dose
-Recommended follow-up period

-Liothryonine (Tri-iodothyronine, T3)
-May be prescribed in post-thyroidectomy patients to minimize the amount of time they need to be off thyroid replacement therapy before an iodine scan; not used as mono-therapy
-Patients should be encouraged to eat a high-fiber diet to reduce the risk of constipation and, if obese, to eat a low-fat diet, at least until he/she is euthyroid

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18
Q

follow up

A

-Once full replacement is achieved and TSH levels are stable, follow-up measurement of TSH is recommended at annual intervals and may be extended to every 2 to 3 years, if a normal TSH is maintained over several years
-It is important to ensure ongoing compliance, however, as patients do not feel any difference after missing a few doses of levothyroxine, this sometimes leads to self-discontinuation

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19
Q

summary of hypothyroid

A

-Common condition caused by inadequate secretion of thyroid hormone
-Hypothyroidism is usually not life-threatening (unless myxedema coma)
-Cardiac enlargement due to dilation and -pericardial effusion (myxedema heart disease) may occur
-Dyslipidemia, a major cause of coronary artery disease
-Serious illness is characterized by non-pitting edema (myxedema) of face and periphery
-Treated by thyroid hormone replacement (levothyroxine)
-Many patients with mild thyroid failure are not diagnosed due to a lack of screening with thyroid-stimulating hormone (TSH) assay among the adult population
-Myxedema Coma - potentially fatal complication

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20
Q

myxedema coma

A

-High mortality rate
-Possible h/o treated hypothyroidism with poor compliance, or the patient may be previously undiagnosed
-Myxedema coma almost always occurs in the elderly
-Somnolence leading to stupor and coma
-Extreme hypothermia: 75.2-90°F (24-32.2°C)
-Hypotension
-Seizures
-Respiratory depression with retention of arterial carbon dioxide
-Severe hyponatremia
-Quiet, distended abdomen due to paralytic ileus
-Goiter or a scar consistent with thyroidectomy should be specifically sought
-Other signs of adult hypothyroidism
-Possible dominant signs in severe disease :
-Frank psychosis (Myxedema madness)
-Severe cerebellar ataxia
-Myxedema heart disease
-Enlarged due to dilation and pericardial effusion

21
Q

precipitating factors: myxedema coma

A

-Hypoventilation, leading to hypoxia and hypercapnia, plays a major role in pathogenesis
-Drugs (especially sedatives, anesthetics, antidepressants)
-Pneumonia, CHF, MI, GI bleeding, or CVA
-Sepsis should also be suspected
-Exposure to cold may also be a risk factor -> warm them slowly
-Hypoglycemia
-Hyponatremia

22
Q

management of myxedema coma

A

-Warmed with blankets – only if < 30º
-But - too rapid warming increases the risk of cardiac arrhythmias
-Airway management and ventilatory support - prevent respiratory failure
-Intravenous levothyroxine
-Parenteral hydrocortisone – prevents adrenal crisis
-Hypothyroidism may worsen prognosis in other critical illness by contributing to hypoventilation, hypotension, hypothermia, bradycardia, and/or hyponatremia
-Hypertonic saline or IV glucose- Warmed fluids -> For hyponatremia or hypoglycemia
-Hypotonic intravenous fluids should be avoided - may exacerbate water retention secondary to reduced renal perfusion and inappropriate vasopressin secretion
-Metabolism of most medications is impaired:
-Sedatives should be avoided or used in reduced doses
-Monitor medication levels

23
Q

certinism

A

-mental and growth retardation and occurs when children who live in iodine-deficient regions are not treated with iodine or thyroid hormone to restore normal thyroid hormone levels during early childhood
-These children are often born to mothers with iodine deficiency, and it is likely that maternal thyroid hormone deficiency worsens the condition
-Concomitant selenium deficiency may also contribute to the neurologic manifestations of cretinism
-macroglosia

24
Q

congenital hypothyroidism

A

-Common enough – approximately 1 in 4000 newborns
-Neonatal screening is performed in most industrialized countries
-The underlying causes of most cases of congenital hypothyroidism are unknown
-Early treatment with thyroid hormone replacement precludes potentially severe developmental abnormalities

25
Q

neonatal/congenital hypothyroidism

A

-At birth: Prolonged jaundice
-Within a few months after birth:
-Hoarse cry
-Constipation
-Somnolence
-Feeding problems

26
Q

neonatal/congenital hypothyroidism

A

-Impaired mental development
-Delayed skeletal maturation - Short stature
-Coarse features with a protruding tongue
-Broad, flat nose
-Widely set eyes
-Dry skin
-Protruding abdomen with an umbilical hernia
-Delayed dentition
-Juvenile/infantile hypothyroidism
-Some signs shared with adult hypothyroidism
-Linear growth retarded
-Delayed puberty
-Delayed union of epiphyses

27
Q

thyroiditis

A

-Autoimmune etiology
-May result from an infection
-May also be iatrogenic in cause
-In some cases (e.g. subacute thyroiditis), this inflammation can result in transient hyperthyroidism caused by thyroid follicle damage and release of preformed thyroid hormone
-In most cases, thyroiditis is self-limiting, and euthyroidism or hypothyroidism eventually occur, depending upon the etiology and phase of the illness

28
Q

acute thyroiditis

A

-Bacterial infection: especially Staphylococcus, Streptococcus, and Enterobacter
-Fungal infection: Aspergillus, Candida, Coccidioides, Histoplasma, and Pneumocystis
-Radiation thyroiditis after 131I treatment
-Amiodarone (may also be subacute or chronic)
-pain is present

29
Q

subacute thyroiditis

A

-Viral (or granulomatous) thyroiditis
-Silent thyroiditis (including postpartum thyroiditis)
-Mycobacterial infection

30
Q

chronic thyroiditis

A

-Autoimmunity: Hashimoto’s thyroiditis, atrophic thyroiditis; focal thyroiditis,
-Riedel’s thyroiditis
-Parasitic thyroiditis: echinococcosis, strongyloidiasis, cysticercosis
-Traumatic: after palpation
-Hashimoto’s thyroiditis - most common clinically apparent cause of chronic thyroiditis
-Riedel’s thyroiditis - rare disorder

31
Q

diff dx of thyroid pain

A

-Acute
-Abrupt onset
-ESR and WBC - ↑
-Thyroid function- Normal [there is leaking of the hormones]
-FNA biopsy - infiltration by PMN’s; culture for organism

-Subacute
-Chronic thyroiditis
-Hemorrhage into a cyst
-Malignancy including lymphoma
-Amiodarone-induced thyroiditis or amyloidosis - rare

32
Q

hashimoto’s thyroiditis

A

-Chronic lymphocytic or Autoimmune thyroiditis
-Most common thyroid disease
-Elevated levels of antithyroid antibodies found
-Familial
-Women : Men – 6:1
-Increased frequency with dietary iodine supplementation
-Exposure to head/neck radiation – increases risk
-Condition generally results in progressive hypothyroidism- > Hyperthyroidism – rare
-Diffusely enlarged
-Firm
-Finely nodular
-May find asymmetric enlargement – one lobe ??malignancy
-C/o neck tightness
-Atrophic gland – fibrotic; 10%; elderly women
-Depression; chronic fatigue
-Xerostomia- dry mouth
-Keratoconjunctivitis-sicca
-Test- Ultrasound guided FNA biopsy

33
Q

hashimoto’s thyroiditis: assoc diseases

A

-Schmidt’s syndrome – adrenal insufficiency
-addisons
-Other autoimmune diseases - Inflammatory bowel disease (IBD); Celiac disease
-Rarely with: Myocarditis; Encephalopathy; Membranous nephropathy
-Turner’s syndrome
-Hepatitis C
-Increased risk of miscarriage in first trimester
-thyroid, adrenals, gonads, parathyroids, and endocrine pancreas, in any combination, along with nonendocrine abnormalities of presumed autoimmune origin, such as vitiligo, alopecia, and pernicious anemia; it occurs primarily

34
Q

hashimotos thyroidits: management

A

-With Hypothyroidism -Levothyroxine
-With large goiter & normal/ ↑ TSH -> T4 – to suppress TSH & shrink goiter
-With minimal gland enlargement and euthyroid state
-Observe
-May develop hypothyroidism years later

-Statins
-Selenium

35
Q

hashimoto’s thyroidits: hyperthyroidism

A

-Due to release of stored hormones
-prompt fall in serum T3
-Synonyms
-“Hashitoxicosis ”
-Painless sporadic thyroiditis
-Postpartum painless thyroiditis
-Mild to severe symptoms
-Propanolol; contrast medications
-Rule out Grave’s disease with RAI uptake

36
Q

riedel’s thyroiditis

A

-Typically occurs in middle-aged women
-Insidious, painless goiter with local symptoms due to compression of the esophagus, trachea, neck veins, or recurrent laryngeal nerves
-Dense fibrosis
-Can extend outside the thyroid capsule
-Thyroid dysfunction is uncommon
-PE: Goiter is hard, nontender, often asymmetric and fixed, leading to suspicion of a malignancy
-Diagnosis: Open biopsy
-Treatment: directed to surgical relief of compressive symptoms
-Tamoxifen – may also be beneficial
-Association between Riedel’s thyroiditis and idiopathic fibrosis at other sites (retroperitoneum, mediastinum, biliary tree, lung, and orbit)

37
Q

suppurative or acute thyroiditis

A

-Rare
-Infection – bacterial
-AIDS patients - Low-grade mycobacterial, fungal, and parasitic infections
-Increased risk - with preexistent disease and immunocompromised or debilitated
-In children and young adults - the most common cause is the presence of a piriform sinus; mostly left sided
-Risk factors in the elderly - A long-standing goiter and degeneration in a thyroid malignancy

38
Q

suppurative or acute thyroidits: symptoms

A

-Abrupt presentation
-Thyroid pain, often referred to the throat or ears
-Small tender goiter that may be asymmetric
-Fever, dysphagia, and erythema – common
-Fluctuation of gland
-Systemic symptoms - febrile illness and lymphadenopathy

39
Q

suppurative or acute thyroidits: management

A

-Management
-Antibiotics
-Surgery – to drain abscess prn
-Complications
-Tracheal obstruction, septicemia, retropharyngeal abscess, mediastinitis, and jugular venous thrombosis
-Uncommon with prompt use of antibiotics

40
Q

subacute thyroiditis

A

-Synonyms
-de Quervain’s thyroiditis
-Granulomatous thyroiditis
-viral thyroiditis

-Etiology
-?viral infection - mumps, coxsackie, influenza, adenoviruses, and echoviruses
-Interleukin-2 therapy
-S/p surgery for hyperparathyroidism

-Silent thyroiditis
-Patients on lithium - rare
-Hyperthyroidism →→ Hypothyroidism
-Thyroid RAI uptake – low during thyrotoxicosis
-Symptoms – mimic manic episode

41
Q

subacute thyroidits: pathophysiology

A

-Characteristic patchy inflammatory infiltrate
-Disruption of the thyroid follicles:
-Leading to increased circulating T4 and T3 and suppression of TSH
-Radioactive iodine uptake is low or undetectable

-Granulomas develop, accompanied by fibrosis
-After several weeks, the thyroid is depleted of stored thyroid hormone and a phase of hypothyroidism occurs -> With low unbound T4 (and sometimes T3) and moderately increased TSH levels
-Radioactive iodine uptake returns to normal or is even increased as a result of the rise in TSH
-Finally, thyroid hormone and TSH levels return to normal as the disease subsides

42
Q

subacute thyroiditis: symptoms

A

-Moderately enlarged, tender thyroid **
-Pain often referred to jaw/ear
-Fever
-Features of thyrotoxicosis or hypothyroidism
-Malaise and symptoms of URTI
-C/o of sore throat
-PE - small goiter that is exquisitely tender!
-Complete resolution is the usual outcome, but permanent hypothyroidism can occur
-Can also be a prolonged course over many months with one or more relapses

43
Q

subacute lab evaluation

A

-Thyrotoxic phase - ↑ T3 & T4 ; ↓ TSH
-Diagnosis confirmed by a high ESR and low radioiodine uptake
-WBC may be increased
-Thyroid antibodies - negative
-Hypothyroid phase - ↓ T3 & T4; ↑ TSH
-Recovery phase – euthyroid
-FNA biopsy

44
Q

subacute management

A

-Relatively large doses of aspirin (e.g., 600 mg every 4 - 6h) or NSAIDs
-Glucocorticoids - gradually tapered over 6 to 8 weeks
-Symptom improvement & ↓ ESR
-Thyroid function should be monitored every 2 to 4 weeks using TSH and unbound T4 levels
-Symptoms of thyrotoxicosis – beta-blockers
-Prolonged hypothyroid phase - levothyroxine

45
Q

silent thyroiditis

A

-Painless thyroiditis, or “silent” thyroiditis, occurs in patients with underlying autoimmune thyroid disease
-Clinical course similar to that of subacute thyroiditis -> except that there is little or no thyroid tenderness
-If 3- 6 months after delivery = postpartum thyroiditis
-Typically, patients have a brief phase of thyrotoxicosis, lasting 2 to 4 weeks, followed by hypothyroidism for 4 to 12 weeks, and then resolution -> Often, however, only one phase is apparent
-The condition is associated with the presence of TPO antibodies antepartum, and is three times more common in women with type 1 diabetes mellitus

46
Q

post partum thyroiditis

A

-Occurs in women soon after delivery
-70% chance of recurrence after subsequent pregnancies
-High levels of thyroid peroxidase antibody (TPO) -> In first trimester or soon after delivery
-Common in women with -> Family hx of Hashimoto’s and Other autoimmune diseases
-‘Michrochimerism
-Hyperthyroidism – begins 1-6 months after delivery; continues for 1-2 months; then hypothyroidism develops
-80% recover function
-50% develop permanent hypothyroidism within 7 years

-Microchimerism: The presence of two genetically distinct and separately derived populations of cells, one population being at a low concentration, in the same individual or an organ such as the bone marrow

47
Q

post partum thyroidits: eval and management

A

-Radioactive iodine uptake is initially suppressed
-Normal ESR
-TPO antibodies present
-Glucocorticoid treatment is not indicated for silent thyroiditis
-Severe thyrotoxic symptoms - Propanolol
-Thyroxine replacement – may be needed; discontinue after 6-9 months
-Annual follow-up thereafter is recommended, as a proportion of these individuals develop permanent hypothyroidism

48
Q

drug induced thyroidits

A

-Patients receiving IFN- , IL-2, or amiodarone may develop painless thyroiditis
-IFN:
-Causes thyroid dysfunction in about 5% of patients
-It has been associated with painless thyroiditis, hypothyroidism, and Graves’ disease

-IL-2, which has been used to treat various malignancies, has also been associated with thyroiditis and hypothyroidism

49
Q

amiodarone induced thyrotoxicosis

A

-Structurally related to thyroid hormone
-Contains 39% iodine by weight
-Typical doses of amiodarone – associated with very high iodine intake
-Effects of Amiodarone:
-Acute, transient suppression of thyroid function
-Hypothyroidism
-Thyrotoxicosis that may be caused by at least three mechanisms

-Rx: D/C Amiodarone; antithyroid drugs; oral contrast agents; Potassium perchlorate; glucocorticoids; Lithium; near total thyroidectomy