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Flashcards in Thyroid disorders Deck (78):

What levels of hormones will you see in hypothyroidism?

TSH: high
T4: low
T3: low


What levels of hormones will you see in hyperthyroidism?

TSH: low
T4: high
T3: high


What is a goiter and what causes a goiter?

- abnormal growth of the thyroid gland
- Most common cause world wide: iodine deficiency
- U.S.: multinodular goiter (seen in elderly), chronic autoimmune (Hashimoto's) thyroiditis, graves


What foods are rich in iodine?

- sea veggies, yogurt, cheese, navy beans, strawberries, potatoes, shellfish, eggs, shrimp, and sardines


What are symptoms of obstructive goiters?

- monotone voice
- dysphagia (difficulty swallowing)
- trachea compression


Work up of a goiter?

- Hx and PE
- obtain TSH: if high measure free T4, most common cause is Hashimoto's thyroiditis, tx appropriately
if low: measure free T4, serum total T3, consider ultrasound, need 34 hr radio iodine uptake scan, multinodular goiter/graves disease most common


Epidemiology of hypothyroidism?

- 3-5% of pop has some form of hypothyroidism
- more common in women than in men
- incidence increases with age
- most common cause: Hashimoto's thyroiditis!!!!
- 3 types: primary, secondary and tertiary


Causes of primary hypothyroidism?

- iodine deficiency
- autoimmune: hashimoto's
- iatrogenic: iodine-131 therapy, thyroidectomy
- post partum thyroiditis
- drug induced: lithium, Amiodarone, antithyroid drugs
- congenital: agenesis, dysgenesis, hypoplastic
- adult onset: normal aging


Causes of secondary hypothyroidism?

- neoplasm
- surgery
- post partum necrosis
- cushing's
- radiation


Causes of tertiary hypothyroidism?

- hypothalamus dysfunction
- hemochromatosis
- sarcoidosis
(abnorm. collection of inflammatory cells)


History of signs and sxs of hypothyroidism

- fatigue
- cold intolerance
- weakness
- lethargy
- wt gain
- constipation
- myalgias
- arthalgias
- menstrual irregularities
- hair loss


Physical findings of hypothyroidism?

- dry, course skin
- hoarse voice
- brittle nails
- periorbital, peripheral edema (myxedema - non pitting edema in the legs)
- delayed reflexes
- slow rxn time
- bradycardia


Dx hypothyroidism?

- TSH will be elevated, this indicates that the thyroid hormone production is insufficient to meet metabolic demands, free thyroid hormone levels are depressed
- can have sub-clinical hypothyroidism where T3, T4 are within normal limits but TSH mildly elevated


Tx of hypothyroidism

- thyroid hormone: can start with lower dose (50-100 mcg QD), elderly: 25-50 mcg and increase gradually
- Levothyroxine (T4) (synthroid): based on bioavailability, cost, safety and ease of monitoring therapy
- should be taken on an empty stomach and wait 30 min. before eating (low bioavailability)
- monitor response with clinical features, TSH


how do you monitor thyroid function in pts with intact HPA?

- follow with serial TSH measurements


How do you monitor thyroid function in pts with pituitary insufficiency?

- measurements of free T4 and T3


How often should you monitor thyroid function?

- every 8-12 weeks
elderly: come in 6 weeks


Why do you decrease dosage in elderly?

- with age, thyroid binding may decrease, and the serum albumin level may decline. In this setting, the Levothyroxine dosage may need to be reduced by up to 20%


Types of hypothyroidism?

- hashiomotos thyroiditis
- myxedema
- subclinical hypothyroidism


Most common form of thyroiditis?

- Hashimoto's thyroiditis
- aka chronic lymphocytic thyroiditis
- can be assoc with non-hodgkins lymphoma


What is Hashimoto's?

- autoimmune disorder
- believed to have genetic basis w/ environmental factors
- more common in women than in men (7:1)
- usually occurs b/t 3-6th decade
- most common cause of hypothyroidism in areas where there is sufficient iodine


What are the thyroid antigens that are present in Hashimotos?

- Thyroglobulen (Tg)
- Thyroid peroxidase (TPO)
- the thyrotropin (TSH) receptor


Precipitating factors of Hashimoto's?

- infection
- stress
- sex steroids, pregnancy
- radiation exposure


Most common signs and sxs of Hashimoto's?

- painless goiter
- fatigue
- muscle weakness
- wt gain
- feeling of fullness in the throat
- neck pain, sore throat
- low grade fever
- hair loss


What will thyroid look like on thyroid scan - iodine marked if there is thyroiditis?

- compared to nromal it wouldn't take up as much of the tracer so it wouldn't be as visible as what a normal thyroid would look like


Dx testing for Hashimoto's?

- labs: TSH, free T4

-imaging: ultrasound to establish goiter size, and radioiodine uptake


Tx of Hashimoto's

- thyroid hormone replacement:
levothyroxine (T4) (Levothyroid or synthroid)
under 60 w/o CAD: 50-100 mcg daily, pregnant women: 100-150 mcg, and over 60 pts with CAD: 12.5-50 mcg
- monitoring of TSH is best and most reliable


What is subclinical hypothyroidism?

- either no sxs or minimal sxs suggestive of hypothyroidism with normal serum free T3 and T4 and elevated serum TSH concentrations


What are some strong indicators that subclinical hypothyroidism will progress ot overt hypothyroidism?

- strong predictors:
Anti-TPO abs
TSH> 20
radioiodine ablation Hx (Grave's disease)
other radiation therapies
progression in about 3-18%/year
- may take years or may rapidly occur


WHo is at risk for subclinical hypothyroidism?

- women
- prior hx of graves or post partum thyroid dysfunction
- elderly
-other AI disease
- family hx of: thyroid disease, pernicious anemia, DM 1


Tx of subclinical hypoparathyroidism

- Levothyroxine therapy: recommended in those pts with positive abs because they are at the greatest risk to progress to overt hypothyroidism
- in the absence of + abs:
asx: TSH 10


What is Myxedema?

Not fully understood but thought to be related to CT proliferation in reaction to increased to TSH levels

- pt usually has hx of hypothyroidism


Who usually gets myxedema, what will they present with?

- pt usually has hx of hypothyroidism
- develops in older adults
- droopy eyelids
- lethargy, fatigue, mental sluggishness
- decreased reflexes
- mucopolysaccharide infiltration of dermal space causes: facial puffiness (facies), periorbital edema, non-pitting pretibial edema


Tx of myxedema?

- thyroid hormone replacement
- levothyroxine (T4)
- doses may be increased by 25 mcg every 1-3 weeks until pt is euthryoid
- monitor TSH


Epidemiology of hyperthyroidism?

- aka thyrotoxicosis or toxic diffuse goiter
- incidence 1-2 cases/1000 a year
- most common cause is Grave's disease:
auto-immune d/o appears suddenly
- body produces abs to receptor for TSH
- annual incidence of Grave's disease is 0.02-0.04%
- occurs most commonly in women b/t ages of 20 and 40


Mist common cause of hyperthyroidism?

- Graves disease
- auto-immune disorder


Etiology of hyperthyroidism?

- common:
toxic adenoma (solitary)
toxic multinodular goiter

- less common:
subacute thyroiditis
hashimoto's thyroiditis with transient hyperthyroid state
postpartum thyroiditis

- rare: struma ovarii (ovarian tumor: presence of thyroid tumor in ovary, made up of displaced thyroid tissue)
hydatiform mole, metastatic thyroid cancer, TSH secreting pituitary tumor, pituitary resistance to T3 and T4
- hyperthyroidism that can't be correlated to the endocrine system is usually a malignancy (small cell carcinoma or carcinoid)


Sxs of hyperthyroidism?

- nervousness
- diaphoresis
- palpitations
- fatigue
- wt loss
- frequent bowel movements


Signs of hyperthyroidism?

- tachycardia
- goiter
- skin changes (pretibial myxedema)
- tremor
- eye signs (exophthalmos)
- conjunctival inflammation
- extraocular muscle dysfunction
- lid lag
- osteoporosis


lab findings of Hyperthyroidism?

- TSH: low
- Free T4: high
- TSI (thyroid stimulating immunoglobulin) may be elevated in Grave's disease
- radioactive iodine uptake will be increased


Tx of hyperthyroid? anti-thyroid drugs

- anti-thyroid drugs:
thioamides - methimazole (tapazole) or propylthiouracil (PTU)
- both act by inhibiting iodine orgnafication
- SEs: common - pruritus, arthralgias, GI distress, metallic taste
rare: agranulocytosis, hepatitis (PTU), aplastic anemia, thrombocytopenia
- want to get baseline: LFTs (CMP), CBC


Radioactive iodine tx for hyperthyroidism?

- msot widely recommended permanent tx of hyperthyroidism
- 80-90% of injected I-131 is absorbed by hyperplastic, toxic thyroid gland w/in 1 day of injection
- can worse Grave's ophthalmopathy transiently
- post tx precautions: limit exposure to others for a week
- pretx: stopping thyroid hormone replacement - high levels of TSH encourage uptake of RI by thyroid
- most common SE: hypothyroidism


Surgical removal for hyperthyroidism

- perm. cure
- used 1% of time - although some graves pts who have surgical removal of their thyroid (can't tolerate meds or refuse radioactive iodine). Other casues of hyperthyroidism can be better suited for surgical tx earlier in disease
- prep of pt before surgery dramatically decreases risk
- PTU or high concentration iodides


Sx tx for hyperthyroidism

- sxs: tachycardia, anxiousness, jitters
- b-blockers: propanolol

- for pts with temp forms of hyperthyroidism (thyroiditis or taking excess thyroid meds), b-blockers may be only tx required
- d/c with sx resolution


Forms of hyperthyroidism?

graves disease
multinodular goiter
factitious hyperthyroidism
thyroid storm


What is Grave's disesase?

- organ specific AI d/o
- body creates circulating abs: common autoimmune abs - anti-TPO and anti-TG abs
- another impt autoab in graves is thyroid stimulating immunoglobulin (TSI)


How does TSI work?

- it is directed toward follicles of TSH receptor and acts as TSH receptor agonist
- similar to TSH, TSI binds to TSH receptor on thyroid follicular cells to activate thyroid hormone synthesis and release, and thyroid growth (hypertrophy)


Who does graves affect the most?

- females: 4:1, ages 20-50
- familial tendency is evident
- spontaneous remission seen in 20-30% of pts


Sxs of graves?

- tetrad of sxs:
nontender, smooth, symmetric thyroid enlargement
- thyrotoxicosis - hyperthyroid state
- exopthalmosis
- pretibial myxedema

- exremely thin digits
- excessive sweating
- older individuals may have apathetic hyperthyroidism: flat affect, wt loss, emotional lability, a-fib, CHF, muscle weakness


Where does pretibial myxedema present?

- lower legs, feet, hands


Labs for Grave's disease?

TSH: low
T4: high
- most specific autoab for autoimmune thyroiditis is an ELISA for TSHR-ab levels
- TSI if elevated helps establish dx of graves
- RAIU (more prominent, more uptake of iodine)


Tx of Grave's disease?

- antithyroid drugs: PTU and methimazole for at least 12-18 months
- B blockers (propranolol)
prevents peripheral conversion of T4-T3
decreases BP and HR
- radioactive iodine (use steroids to decrease worsening of exophthalmos with use of RAI)
- surgery


What is a multinodular goiter or "Plummers disease"?

- characterized by functionally autonomous nodules
- disease of older individuals
- common in areas of iodine insufficiency
- caused by hyperplasia of follicular cells whose activity becomes independent of TSH: may present with subclinical hyperthyroidism


Dx of multinodular goiter?

- suppressed TSH
- markedly elevated T3
- mod. elevaed T4
- thyroid scan with mult. functioning nodules
will see multiple darkened areas on scan - nodules


What is factitious hyperthyroidism?

- ingestion of levothyroxine by euthyroid pts
- AKA thyrotoxicosis factitia
- may be iatrogenic (providers fault)
- may be seen in health care workers, dieters, body builders...munchausen syndrome
- usually an attempt to lose wt
- T3 and T4 are high and TSH is low as is serum thyroglobulin concentration



- elevated T3 and/or T4
- sometimes due to inflammation of thyroid
- can occur after ingestion of exogenous hormones (buying levo OTC in Mexico as wt loss agent
- usually no hx of hyperthyroid condition


What is a thyroid storm?

- life threatening crisis, a rare endocrine emergency
- precipitating factors:
infection (usually respiratory)
diabetic ketoacidosis
physical or emotional trauma
manipulation during thyroidectomy


Clinical features of a thyroid storm?

- very high fever
- CV effects
- CNS effect
- Nausea and vomiting


Tx of thyroid storm?

- rapid dx and tx
- peripheral cooling (cold packs and cooling mattress)
- replace fluids, glucose, and electrolytes
- propanolol to block effects of T4 on CV function
- glucocorticoids to correct adrenal insufficiency and to inhibit peripheral conversion of T4 to T3
- propylthiouracil (PTU) and methimazole to block thyroid synthesis


What is thyroiditis?

- classified as acute, subacute, and chronic
- usually presents clinically as hyperthyroidism due to leakage of preformed TH though most pts ultimately develop hypothyroidism
- can be distinguished from other causes of thyroiditis because RAIU is low!!!!!!!


Acute thyroiditis?

- a rare complication of septicemia
- presents with fever, redness of skin over thyroid and TENDERNESS of thyroid
- blood cultures are negative, aspiration of thyroid gland may be tried to ID the organism
- usually tx with IV abx, though occasionally I&D of gland


Subacute thyroiditis?

- de Quervain's thyroiditis or granulomatous thyroiditis
- probably secondary to viral infection
- characterized by fever and anterior neck pain, exquisitively tender thyroid gland
- ESR is high and thyroid scan shows little or no uptake of radioiodine
- tx of choice: sx
- complete resolution of sxs in 90% of pts within months


Postpartum (subacute lymphcytic thyroiditis)

- occurs in 5-10% of women post partum
- onset is within 3-12 months post delivery
- presence of TPO abs increases risks
- increased risk of reoccurrence with subsequent pregnancies
- eventually resolves (could take months)
- 25-20% will progress to hypothyroidisim within 5 years of delivery


Presentation of post partum (subacute lymphocytic) thyroiditis

- thyroid gland is NONTENDER
- low uptake of RAI


Tx of postpartum thyroiditis?

- propanolol for tremors and tachycardia
- if hypothyroidism develops: Levo for 6 months to restore normal fxn
- those who go on to develop perm. hypothyroidism will have to take levo for life


iodine induce (jod-basedow) thyroiditis?

introduced by contrast agents for angiography or CT scan
- low uptake of RAI
- absence of antithyroid abs


Amiodarone induced thyroiditis?

- iodinated drug with antiarrhythmic and antianginal properties
- type 1: occurs in pts with underlying thyroid disease
- type 2: occurs in normal thyroids


Chronic thyroiditis?

- Hashimotos thyroidits: hypothyroidism
- riedel's struma (invasvie fibrous thyroiditis) rare form of thyroiditis seen in middle aged women. The gland is stony hard and adherent to surrounding structures and amy cause sxs of compression (dysphagia, dyspnea or hoarseness)
- tx Tamoxifen, steroids


What are thyroid nodules most of the time?

- most often benign neoplasms from follicular epithelium
- most common endocrine problem in US
- often painless, often discovered during a routine PE
- appears as cold nodules on RAIU scan


Solitary thyroid nodule?

- common: seein in 50% of pop at autopsy
- most pts have normal thyroid fxn
- since a small % of nodules are malignant, practical approach to detet and eval. these lesions


High risk factors for malignant solitary thyroid nodules?

- Hx: head and neck irradiation, exposure to nuclear radiation, recent onset, rapid growth, young age, male sex, familial incidence
- physical: hard consistency, fication, lymphadenopathy, vocal cord paralysis, distant metastasis
- lab/imaging: elevated calcitonin, cold nodule, solid lesion on ultrasound
- levothyroxine therapy: no regression
- fine, irregular and fixed


Features that favor a benign thyroid nodule?

- family hx of hashimoto's
- family hx of benign nodule
- sxs of hypothyroidism or hyperthyroidism
- pain or tenderness assoc with nodule
- soft, smooth and mobile
- multinodular w/o prominent nodule
- warm nodule on thyroid scan
- simple cyst on US


Thyroid cancer

- accounts for 1% of all malignant neoplasms
- 5-10/100000 / year
- 3:1 female to male
- may present as painless swelling in region of thyroid
- dx is made by FNA cytology
- radioactive iodine scanning usually shows malignancies to be hypofxning (cold)


Types of thyroid cancer?

papillary: 75% (most common)
follicular: 10-20%
medullary: 5%
anaplastic: less than 5%

predisposing factors: familial medullary carcinomas occur in MEN II
- exposure to ionizinng radiation
- preexisting thyroid disease


Papillary carcinoma?

- most common thyroid cancer
- occur at any age, most common in 30s, assoc with previous exposure to radiation, well diff, slow growing
- Hx: mostly asx
- PE: painless neck mass or metastatic disease to cervical lymph nodes
- labs: thyroglobulin levelas are elevated
- prog: 10 year survival rate up to 85%
- tx: thyroidectomy in conjunction with radioactive iodine
- lifetime levo


Follicular carcinoma?

- slow growing
- spreads to regional nodes
- hematogenous spread to lung or bone
- prognosis depends on degree of vascular invacsion and metastases
tx is same as papillary, remove and radio, levo


Medullary carcinoma:

- familial affiliation
- equal occurrence in both sexes

- 30-6o yo
- occur in C cells in thyroid
- often presents as nodule in upper half of thyroid
- calcitonin is unique tumor marker for medullary cancer, although they remain eucalcimic
- sometimes part of MEN syndrome
- tx is surgical removal


Hurthle cell carcinoma?

- very rare
- usually classified as follicular thyroid cancer
- can be benign or malignant
- median age: 50
- cell has distinctive look under microscope
- tx: surgical rmoval