Thyroid Flashcards
Normal Thyroid
- Weight
- Gross look
- Histo
- 20-25 g
- right lobe, isthmus, left lobe
- follicle lined by cuboidal to low columnar follicular cells; contain parafollicular or “C” cells which secrete calcitonin
Hypothalamus-Pituitary-Thyroid Axis
- Hypo releases
- Pituitary releases
- Thyroid releases
- Inhibition
- Actions of T3/T4
- TRH onto pituitary
- TSH onto Thyroid
- T4
- Feedback inhibition by T3/T4 on Pituitary and Hypothalamus
- stimulation of protein synthesis; upregulation of carb and lipid metabolism; increase basal metabolic rate; critical role in the development of brain in fetuses and neonates
Thyrotoxicosis
- Define
- Most common cause
- hyper metabolic state due to increased circulating levels of thyroid hormones
- hyper functioning of the thyroid gland
Thyrotoxicosis Disorders
- Associated w/ Hyperthyroidism: Primary
- Associated w/ Hyperthyroidism: Secondary
- Not associated w/ Hyperthyroidism
- Diffuse toxic hyperplasia (Grave’s Disease), Hyperfunctioning (toxic) multinodular goiter, Hyperfunctioning (toxic) adenoma, iodine induced hyperthyroidism, neonatal thyrotoxicosis associated w/ maternal Grave’s disease
- TSH secreting pituitary adenoma
- Granulomatous (deQuarvain) thyroiditis (painful); subacute lymphocytic thyroiditis (painless); struma ovarii (ovarian teratoma w/ ectopic thyroid); factitious thyrotoxicosis (exogenous thyroid intake)
Hyperthyroidism/Thyrotoxicosis: Clinical Manifestations (10)
11. Due to what?
- Increased BMR- soft, warm, flushed skin
- heat intolerance and excess sweating
- characteristic weight loss despite increased apetite
- CV- increased CO, tachycardia, palpitations, cardiomegaly, arrhythmias (uncommon) especially atrial fibrillation; development of low output heart failure;
- Neuromuscular: nervousness, emotional lability, insomnia, muscular weakness, fine tremor of hands
- Proximal muscle weakness and decreased muscle mass
- GI: hypermotility, malabsorption and diarrhea
- Ocular: wide staring gaze, lid lag
- Thyroid opthalmopathy (exophthalmos)
- Bone resorption w/ osteoporosis
- excess of thyroid hormones and over activity of sympathetic nervous system
Hyperthyroidism: Dx
- What 3 things are measured?
- Describe TRH stimulation test
- Describe Radioactive Iodine Uptake test
- What does diffuse uptake indicate?
- Localized uptake?
- reduced uptake?
- TSH (usually decreased); T4 (usually increased); T3 (rare pts w/ nl or reduced T4 but elevated T3)
- injection of TRH; normal rise in TSH exclude pituitary associated hyperthyroidism
- used after dx of thyrotoxicosis
- Graves
- toxic adenoma
- thyroiditis
Hypothyroidism
- Define
- Primary Causes (7)
- Secondary Causes (2)
- hypermetabolic state secondary to inadequate levels of thyroid hormones
- Developmental, Thyroid hormone resistance syndrome, post ablative, autoimmune hypothyroidism, iodine deficiency, drugs, congenital biosynthetic defect
- Pituitary Failure, Hypothalamic failure
Hypothyroidism
- Most common cause of what physical symptom?
- Worldwide congenital hypothyroidism most often due to what?
- Most common cause where (2) isn’t a problem?
- Other clinical manifestations (2)
- enlargement of the gland (goiter)
- endemic iodine deficiency in diet
- chronic autoimmue thyroiditis (Hashimoto’s)
- cretinism and myxedema
Cretinism
- Define
- Cause
- What determines the severity?
- Symptoms
- hypothyroidism in infants or early childhood
- secondary to iodine deficiency (endemic) or rarely from inborn errors in metabolism
- timing of the deficiency; if maternal thyroid deficiency occurs before fetus develops thyroid that develops own T3/T4, will be more severe
- Impaired development of skeletal muscles and CNS
Myxedema
- Define
- Symptoms (6)
- What does it do to blood lipids?
- adult hypothyroidism
- gradual slowing of mental and physical activity
- fatigue, lethargy, apathy, slowed speech
- cold intolerance, reduced sweating
- overweight, constipation
- periorbital edema, thick coarse skin, enlarged tongue; (deposition of glycosaminoglycans)
- Reduced cardiac output causes shortness of breath and decreased exercise capacity
- promotes atherogenic profile (increased total cholesterol and LDL) –> adverse CV mortality rates
Hypothyroidism: Lab findings
- T4
- TSH
- What is seen in primary hypothyroidism?
- Secondary?
- decreased
- most sensitive test for hypothyroidism
- increased TSH (thyroid not making enough T4)
- decreased/normal TSH (suggest pit tumor, necrosis; not enough TSH being produced)
Thyroiditis
- Define
- Causes with pain (2)
- causes w/o or w/ little pain
- inflammation of thyroid gland
- infectious thyroiditis, subacute granulomatous thyroiditis (De Quervain thyroiditis- most common cause of painful thyroiditis)
- Subacute lymphocytic thyroiditis; Reide’s thyroiditis; Hashimoto’s thyroiditis
Hashimoto Thyroiditis
- Define
- What areas get it?
- What age group is it found in?
- Is there a genetic component?
- 3 Mechanisms
- autoimmune destruction of the thyroid gland: hypothyroidism
- areas without iodine deficiency
- 45-65
- yes
- T cell-mediated cytotoxicity; Activated macrophages causing thyrocyte injury, Antibody-dependent cell-mediated immunity
In general, which gender gets thyroid disorders/neoplasms more often?
Women
Hashimoto Thyroiditis
- Labs show antibodies to what? (3)
- Gross look
- Histo look
- Thyroglobulin and Thyroid peroxidase (TPO-most common); TSH receptor, Iodine receptor
- diffusely enlarged gland with intact capsule; well demarcated from adjacent structures; cut surface is pale, yellow tan, somewhat nodular and firm
- parenchyma infiltrated by mononuclear inflammatory cells; Hurthle cells/oncocytes line Thyroid follicles and have abundant granular pink cytoplasm
Hashimoto Thyroiditis: Clinical Course
- What happens physically?
- How quickly does hypothyroidism develop?
- what do some pts develop?
- Increased risk of developing what diseases (3)
- painless enlargement of gland w/ some degree of hypothyroidism
- gradually
- transient hyperthyroidism (due to disruption of follicles and release of T3/T4); gradually hypothyroidism sets in
- Increased risk of other autoimmune disease
- Increased risk of developing Non Hodgkin B cell lymphoma
- May have increased risk of developing papillary carcinomas
Subacute/Granulomatous (De Quervain) Thyroiditis
- Etiology
- Clinical Course?
- Histo look:early
- Histo look: late
- Gross look
- Viral or post-viral inflammatory response: viral Ag or virus-induced host tissue damage stimulates formation of cytotoxic T cells which then damage the thyroid follicular cells
- self-limited; pt is asymptomatic after acute stage
- disruption of follicles w/ collections of neutrophils forming microabscesses
- aggregates of lymphocytes. plasma cells, and activated macrophages around damaged thyroid follicles;
- uni/bilateral, enlarged and firm w/ intact capsule
Granulomatous (De Quervain) Thyroiditis
- Commonly Causes what
- Does the thyroid enlarge?
- What is commonly in pt’s history?
- How long does hyperthyroidism last?
- What is elevated in hyperthyroidism phase?
- How long does it last?
- thyroid pain
- variable
- upper respiratory infection
- 2-6 weeks
- elevated T3 and T4; diminished TSH, radioactive iodine uptake is diminished
- 6 to 8 weeks
Subacute Lymphocytic Thyroiditis
- What causes pt to come in?
- Who gets it?
- Etiology
- Clinical Course
- Gross look
- Histo look
- mild hyperthyroidism, goitrous enlargement of thyroid, or both
- middle aged women; can also occur in post-partum period
- variants of hashimoto
- majority of pts are euthyroid by 1 year, 1/3 progress to overt hypothyroidism over 10 yrs
- mild enlargement
- lymphocytic infiltration w/ germinal centers; no fibrosis or hurthle cell metaplasia
Riedel Thyroiditis
- Etiology
- Histo look
- Gross look
- May be associated with what?
- unknown
- extensive fibrosis involving the thyroid and contiguous neck structures
- hard and fixed mass, simulating cancer
- idiopathic fibrosis at other sites like retroperitoneum
Grave’s Disease
- How common is it?
- Symptoms
- Etiology
- most common cause of endogenous hyperthyroidism (1.5-2% of US women)
- Triad of Findings: hyperthyroidism due to diffuse hyperfunctional enlargement of thyroid
Infiltrative Opthalmopathy - exophthalmos
Infiltrative Dermopathy- pretibial myxedema (most pts present before this develops) - autoimmune disease: Thyroid stimulating immunoglobulin (TSI) binds to TSH receptor and mimics its action (relatively specific for Graves)
Thyoid growth stimulating hormone (TGI)- causes proliferation of the follicular epithelium
TSH-binding inhibitior immunoglobulin (TBII)
Graves Disease
- Gross Look
- Histo look
- symmetrically enlarged, >80g, soft meaty appearance on cut surface
- crowded and tall follicular cells; formation of small papillae filling the lumen of the follicles; papillae lack fibrovascular cores; pale colloid with scalloped margins; lymphoid infiltrate w/ germinal centers common
Graves Disease: Clinical Manifestations (5)
6. Risk of what?
- Thyrotoxicosis
- Thyroid gland enlargement
- Wide staring gaze and lid lag- sympathetic overactivity
- Infiltrative ophthalmopathy- Exophthalmos (accumulation of loose connective tissue behind the eyeball, doesn’t go away w/ treatment)
- Infiltrative dermopathy- pretibial myxedema
- Risk of other autoimmune diseases
Pretibial Myxedema
- Where does it occur?
- What is it?
- what disease is it associated with?
- skin overlying the shins
- scaly thickening and induration
- Grave’s disease
Grave’s Disease: lab findings
- What are the levels of T3, T4, and TSH?
- What happens on radioactive iodine uptake?
- increased free T3 and T4; decreased TSH
2. diffuse uptake
Goiter
- Define
- How does it develop?
- What does it start out as?
- What does it become?
- When is it endemic?
- What gender gets the sporadic type? When?
- enlargement of the thyroid
- impaired synthesis of T3 and T4; increased TSH –> hyperplasia and hypertrophy of follicular epithelium
- diffuse (simple)
- becomes multinodular
- > 10% of population, seen in mountainous regions
- females, at puberty
Diffuse/Nontoxic Goiter
- What is it?
- Cut surface?
- Histo look
- enlargement of the entire gland w/o producing nodularity; diffuse symmetric enlargement
- brown, glassy, translucent
- 2 phases: Hyperplastic phase- enlarged thyroid gland w/ crowded follicular cells
Colloid involution- distended follicles
flattened epithelium
Diffuse Nontoxic Goiter
- What are Thyroid hormones/TSH?
- Complications due to?
- What will it become?
- normal T3/T4; elevated or upper normal TSH
- mass effect, may press on trachea, esophagus, may also cause cosmetic disfigurement
- Multinodular Goiter
Multinodular Goiter
- What is it?
- How does it develop?
- Who gets it?
- Is it toxic?
- What can happen to cells w/in a nodule?
- asymmetric enlargement w/ numerous nodules
- evolves from diffuse goiters over many years due to repeated episodes of hyperplasia and involution (hemorrhage and fibrosis –> nodules)
- older adults, but similar epidemiology to Diffuse
- may be toxic or non-toxic
- Cells may become autonomous and continue proliferating
Multinodular Goiter
- complications
- Gross look
- Cut section
- Histo look
- mass effect; may press on trachea –> snoring/stridor; may cause dysphagia
- asymmetric, multilobated gland; may be very large; one lobe may be more involved than the other; may become intrathoracic or “plunging” behind sternum and clavicles
- irregular nodules containing gelatinous colloid; foci of fibrosis
- Colloid rich follicles lined by flattened inactive epithelium; areas of follicular hyperplasia; lacks a capsule
Multinodular Goiter
- What happens to T3 and T4?
- What may develop?
- Malignancy risk?
- What happens on radioactive iodine uptake?
- what test is done to determine if its malignant?
- normal
- minority develop toxic multinodular goiter due to development of an autonomous nodule
- t take it up
- fine needle aspirations
Thyroid Neoplasms
- Are they mostly indolent or aggressive?
- What kinds of nodules/pts are more likely to be neoplastic?
- What history is associated w/ increased incidence of thyroid malignancy?
- mostly indolent
2. single nodules, young pts, males, nonfunctioning nodules
Follicular Adenoma
- Describe it
- What 3 mutations are important?
- Gross look
- discrete solitary masses derived from follicular epithelium
- RAS, PAX8-PPARG fusion gene, mutation in TSH receptor signaling pathway
- solitary, encapsulated, spherical; gray-white to red brown mass; may have areas of hemorrhage, necrosis, or calcification
Follicular Adenoma
- Histo look
- What warrants investigation into follicular carcinoma on histo?
- What is seen on histo in Hurthle cell/oxyphil/oncocytic adenoma?
- neoplastic cells arranged in closely packed follicles;
demarcated from adjacent thyroid parenchyma by a well defined capsule;
uniform small follicles which contain colloid; - extensive mitotic activity, necrosis, high cellularity;
- follicular adenoma w/ cells w/ abundant pink cytoplasm due to presence of many mitochondria (not clinically different from normal follicular adenoma)
Follicular Adenoma
- What is the important feature?
- Why?
- What is required for accurate diagnosis?
- What can you say with a small sample?
- capsule
- differentiates adenoma from carcinoma (along w/ vascular invasion)
- histo exam of entire nodule; can’t use fine needle aspiration
- That it is a follicular neoplasm (can be adenoma or carcinoma)
Follicular Adenoma
- How does it present?
- What is seen on radioactive iodine scan?
- What occurs rarely?
- Treatment?
- Prognosis
- painless asymptomatic mass, may produce local symptoms due to mass effect
- usually cold
- rarely is a functioning toxic adenoma
- lobectomy
- excellent, does not recur or metastasize
Thyroid Carcinomas
- How common is it?
- Who gets it?
- Linked with what?
- Major subtypes
- uncommon
- female in middle age; males and females in childhood/late adult life
- ionizing radiation and dietary iodine deficiency; genetic events
- Papillary Carcinoma, Follicular Carcinoma, Medullary Carcinoma, Anaplastic Carcinoma
Papillary Carcinoma
- How common is it?
- common presentation
- Etiology
- Gross look
- What does cut surface show?
- most common thyroid cancer
- 40 y/o female w/ neck mass; (age 25-50)
- accounts for majority of thyroid cancers associated with hx of radiation exposure
- solitary or multifocal; may be well encapsulated or infiltrative; has foci of fibrosis and calcification;
- papillary structures
Papillary Carcinoma
- Histo look
- What does the nucleus look like? (3)
- What does the nucleolus look like?
- What else is present on histo?
- Branching papillae with fibrovascular cores lined by multiple layers of cuboidal to columnar epithelium
- longitudinal nuclear grooves (lines along long axis of nucleus);
ground glass or Orphan Annie eyed nuclei (due to finely dispersed chromatin)
Intranuclear cytoplasmic inclusions (invaginations of the cytoplasm into the nucleus) - marginated to the periphery and close to nuclear membrane
- Psammoma bodies: calcifiled lamellated concretions seen in the cores of papillae
Papillary Carcinoma
- What is the follicular variant (FVPTC)?
- What is the Tall Cell variant? Prognosis?
- Who gets the Diffuse Sclerosing variant?
- What is a papillary microcarcinoma?
- diagnosed based on nuclear features; usually encapsulated, lower incidence of LN invasion and metasasis; good prognosis
- tall columnar cells with intense eosinophilic cytoplasm lining the papillary structures, aggresssive
- occurs in younger individuals
Papillary Carcinoma
- Presentation
- How is it diagnosed?
- Treatment?
- Prognosis?
- What does prognosis depend on?
- Genetic Mutations
- asymptomatic thyroid nodules, LN metastasis; cold on radioiodide uptake
- fine needle aspiration cytology
- Total thyroidectomy w/ excision of abnormal lymph nodes
- Good
- age, extrathyroid extension, distant mets; NOT isolated cervical lymph node metastasis
- RET/PTC (20-40%); BRAF (33-50%)
Follicular Carcinoma
- How common?
- When does it present?
- HIgher in what areas?
- Gross look
- second most common thyroid cancer
- older, 40 to 60
- iodine deficient areas
- single, well circumscribed nodule, light tan appearance, may extend beyond capsule; may have area of hemorrhage
Follicular Carcinoma
- Microscopic look
- Possible variants
- What does it look like when it invades?
- It is significant if the tumor invades what?
- fairly uniform follicular cells forming follicles containing colloid; may have nests of cells w/ less apparent follicular differentiation; no psammoma bodies
2 . Hurthle cell or oncocytic variant (granular pink cytoplasm) - mushrooming of the tumor through the full thickness of the capsule; requires extensive sampling of the tumor capsule interface;
- vessels in the capsule or beyond; not if it invades vessels w/in the tumor
Follicular Carcinoma
- Presentation
- How does it spread? Where?
- Treatment
- What does prognosis depend on?
- Prognosis
- Genetic Events
- slowly enlarging painless nodule; cold on scintiscans
- hematogneous to bone, lungs, liver
- total thyroidectomy w/ radioactive iodine
- extent of invasion
- > 90% have 10 yr survival
- PI3K/AKT (33-50%); PAX8/PPARG fusion product (33-50%)
Medullary Carcinoma
- What kind of neoplasm? Derived from what cells?
- How common?
- What can it do?
- What causes 30% of them?
- When do these 30% present?
- How do these 30% present?
- neuroendocrine; parafollicular or C cells
- 5% of thyroid neoplasms
- secrete calcitonin or other polypeptide hormones like ACTH or VIP
- MEN syndrome 2A or 2B
- first decade (sporadic- 4th or 5th decade)
- multiple; sporadic-single
Medullary Carcinoma
- Gross look
- Histo look
- What do familial medullary cancers have?
- What does Congo Red Stain do?
- solid grey-tan tumor w/o well defined capsule; infiltration of adjacent thyroid parenchyma; larger lesions w/ foci of hemorrhage and necrosis
- spindle cells forming nests; acellular amyloid deposits derived from calcitonin;
- prominent clusters of C cells
- demonstrates amyloid; imparts reddish color; gives an apple green birefringence under polarized light
Medullary Carcinoma
- Presentation
- How may people with MEN present?
- When is it more aggressive?
- Treatment
- 2 Tumor Markers
- What may be done in asymptomatic MEN pts?
- mass, may be asymptomatic; may present w/ paraneoplastic syndromes like diarrhea (VIP), Cushing syndrome (ACTH)
- may have endocrine neoplasms in other organs
- when it arises in MEN 2B pts
- total thyroidectomy
- Calcitonin (does not cause hypocalcemia) and CEA (used as tumor markers)
- prophylactic thyroidectomy
Anaplastic Carcinoma
- Age it shows up?
- Prognosis
- Histo look
- What immunohistochemical stain is used?
- mean is 65 years
- poor; mortality is almost 100% in 1 year
- highly anaplastic cells: spindle cells, giant cells; foci of papillary or follicular differentiation may be present; mitotic figures
- stain for cytokertain; may not stain for thyroglobulin
Anaplasit Carcinoma
- Presentation
- How far has it spread at presentation?
- Symptoms
- Therapy
- When does death occur?
- Genetic event
- rapidly enlarging bulky mass
- beyond thyroid into adjacent structures
- dyspnea, dysphagia, hoarseness, cough (Due to compression of neck structures)
- no effective therapy
- usually within 1 year due to compromise of vital structures
- inactivation of p53 or activating mutations of beta catenin
Thyroglossal duct/cyst
- Define
- How does it present?
- Histo look
- complication?
- incomplete atrophy of the duct where thyroid began in fetus
- as a midline cyst/anterior mass; at any age
- lined w/ benign epithelium; normal thyroid and lymphocytes in the wall
- infection w/ risk of abscess formation