Exam 1 Flashcards
What are the discrete endocrine functional glands?
Pituitary, pineal, thyroid, parathyroid, adrenals
What are the glands with endocrine and exocrine function?
Kidney, pancreas, testes, ovaries, placenta
What type of tissue makes up the anterior lobe (adenohypophysis) of the pituitary?
Glandular epithelial tissue
What type of tissue makes up the posterior lobe (neurohypophysis) of the pituitary?
Neural secretory tissue
Functions of the pituitary gland photos/image
The anterior pituitary:
• receives Neurosecretory cell info from the ventral hypothalamus
• is composed of the pars distalis, intermedia, and tuberalis
• stains darkly
The posterior pituitary:
- receives info from the paraventricular nucleus (oxytocin) and the supraoptic nucleus (ADH) of the hypothalamus
- has the pars nervosa, and releases oxytocin/vasopressin
- stains lightly
Anterior pituitary originates from where embryologically?
Oropharynx ectoderm via rathke’s pouch
Posterior pituitary derives from where embryologically?
Neuroectoderm via infundibular process
Components of the hypophysis (pituitary) and their derivation
Image/graph/table
What is the blood supply of the pituitary?
- Superior hypophyseal arteries from the internal carotid/posterior communicating artery of circle of Willis supplying the pars tuberalis, median eminence, infundibulum
- Inferior hypophyseal artery from the internal carotid arteries supplying the pars nervosa
What part of the pituitary gland has no direct arterial blood supply?
Anterior lobe: rather, supplied by superior hypophyseal artery —> portal veins —> secondary plexus of hypophyseal portal system
What layer of the pituitary gland contains large vesicles with colloid material?
Pars intermedia
Basophils and acidophils are found in what layer of the pituitary gland?
Pars distalis (stains darkly)
Chromophobes are found most commonly in what layer of the pituitary gland?
Pars intermedia
Pituicytes are found in what layer of the pituitary gland?
Pars nervosa— stand slightly, resembles neuronal tissue
What cells are the acidophils?
1. Somatotropes (GH, STH, acidophilic secretory vesicles)
2. Mammotropes (prolactin, acidophilic secretory vesicles, increase in pregnancy)
What cells are the basophils?
- Thyrotropes (TSH)
- Gonadotropes (FSH, LH, ICSH)
- Corticotropes (ACTH, MSH)
What is a Rathke cyst?
Remnants of a Rathke pouch. Follicles lined by cuboidal epithelium and filled with colloid. Found in the pars intermedia
What part of the pituitary gland encircles the infundibulum?
Pars tuberalis: highly vascularized area, superior hypophysis arteries terminate here to form the primary plexus of portal system — contains FSH, LH
The pars nervosa of the posterior pituitary contain neurosecretory vesicles that store what?
Oxytocin and vasopressin/ADH That can accumulate and dilated terminals (Herring bodies) adjacent to capillaries
Cell of the pars nervosa posterior pituitary image
What are the hypothalamic hormones that stimulate the anterior pituitary?
- Thyrotropin releasing hormone (TRH)
- Corticotropin releasing hormone (CRH)
- Gonadotropin releasing hormone (GnRH)
- Growth hormone releasing hormone (GHRH)
What are the hypothalamic hormones that inhibit the anterior pituitary?
- Dopamine (non-peptide)
- Somatostatin (growth hormone inhibiting hormone, GHIH)
Anterior pituitary hormone targets:
• GnRH —> FSH/LH —> ovary/testis
• GHRH —> GH —> liver/all tissue
• somatostatin —| GH
• TRH —> TSH —> thyroid
• TRH —> prolactin —> breast
• dopamine —| prolactin
• CRH —> ACTH —> adrenal cortex
What is thyroid stimulating hormone (TSH)?
• synthesis/secretion stimulated by TRH from hypothalamus
• stimulates growth of the thyroid gland and secretion of thyroid hormones such as T3 and T4
What is luteinizing hormone (LH)?
• synthesis/secretion stimulated by GnRH from the hypothalamus
• promotes estrogen/progesterone synthesis in ovaries and promotes testosterone synthesis in testes
What is follicle stimulating hormone (FSH)?
• synthesis/secretion stimulated by gonadotropin releasing hormone (GnRH) from hypothalamus
• stimulates follicle growth in ovaries and spermatogenesis in testes
What is adrenocorticotropin hormone (ACTH)?
• synthesis/secretion stimulated by corticotropin releasing hormone (CRH) in the hypothalamus
• stimulates corticosteroid production by the adrenal cortex (cortisol, etc.)
ACTH is synthesized from what?
Precursor polypeptide POMC (proopiomelanocortin)
What is present on ACTH N-terminus that can result in hyperpigmentation with excessive ACTH production?
Alpha-MSH (melanocyte-stimulating hormone)
~ this would be considered a secondary hypercortisolism
What is prolactin?
• structurally homologous to growth hormone, its secretion is under tonic inhibition by dopamine
• secretion stimulated by infant sucking and TRH
• promotes breast development, lactation, inhibits ovulation via inhibition of GnRH
What inhibits prolactin’s effect on lactation until birth?
Placental progesterone
What is a prolactinoma?
• most common functioning pituitary tumor leading to a hyper secretion of prolactin —> induces lactation, inhibits GnRH, decreases FSH and LH, leads to decreased progesterone/estrogen and testosterone —> amenorrhea, infertility, impotence, gynecomastia
What is the treatment for a prolactinoma?
- Dopamine agonist is the first line (bromocriptine, cabergoline) because it inhibits prolactin secretion
- Surgery due to increased to ICP/mass effect
What is growth hormone (GH) / somatropin/somatotropic hormone?
• structurally homologous to prolactin, the main function is to promote linear growth
• important in adolescence
What inhibits/stimulates growth hormone?
• stimulated by release of GHRH, exercise, trauma, and acute hypoglycemia
• inhibited by somatostatin
• decreased by age, disease, glucose
What does growth hormone stimulate the liver to produce?
insulin like growth factor-1
• increased protein synthesis, fat utilization
• decreased glucose uptake
What is released in response to hypoglycemia?
Growth hormone (GH)
• increases serum glucose levels by promoting glycogenolysis, gluconeogenesis, lipolysis, ketogenesis
Gigantism and acromegaly are diseases of what hormone?
growth hormone, GH
• gigantism: in children, acting on epiphyseal plate
• acromegaly: adults, acting on fused growth plate cartilage
What other conditions are gigantism and acromegaly associated with?
• enlarged liver and heart
• peripheral neuropathy secondary to nerve compression
• glucose intolerance and diabetes
• amenorrhea, impotence
What is the diagnosis of gigantism/acromegaly?
• increased serum IGF-1
• Oral glucose tolerance test fails to suppress GH
What are the treatments of acromegaly/gigantism
• surgical removal of pituitary
• octreotide: somatostatin analog
• bromocriptine: DA agonist
• pegvisomant: GH receptor antagonist
What are the functions of oxytocin?
• promotes contractions of the uterine myometrium during labor
• stimulates contractions of the mild epithelial cells in the breast (milk production)
What stimulates/inhibits oxytocin?
• stimulate: cervix dilation, suckling of infant
• inhibit: fear, pain, noise, fever
Diabetes insipidus is a defect in what?
Anti-diuretic hormone:
- Central DI: absent/insufficient ADH release (pituitary problem)
- Nephrogenic DI: normal ADH secretion, kidneys unresponsive (renal resistance)
What will a vasopressin challenge distinguish between?
Central DI and nephrogenic DI. Central DI will respond positively to the administration of vasopressin (Tx), and nephrogenic will not (needs thiazide diuretics)
What is SIADH?
Syndrome of inappropriate secretion of antidiuretic hormone: ADH in the absence of hyperosmolarity—> inability to dilute urine—> euvolemic hyponatremia
~ tx: water restriction
What drugs stimulate growth hormone, GH?
- Somatotropin: recombinant hGH
- Mecasermin: recombinant IGF-1
What medication’s decrease/inhibit growth hormone (GH)?
- Octreotide: somatostatin receptor agonist
- Pegvisomant: GH receptor antagonist
- Bromocriptine: dopamine D2 receptor agonist
What are the clinical applications of somatotropin?
• replacement in GH deficiency
• increased final adult height in children with conditions of short stature
• wasting associated with AIDS/malignancy
• short bowel syndrome
What are the side effects of somatotropin?
• edema
• hyperglycemia
• decreased insulin sensitivity
• thickening of bones, progression of scoliosis
• carpal tunnel syndrome
What are the clinical applications and side effects of Mecasermin?
• clinical application: replacement in IGF-I deficiency that is not responsive to somatotropin
• side effects: hypoglycemia, intracranial HTN, increased liver enzymes
What are the clinical applications of octreotide in the relation to growth hormone?
• acromegaly
• hormone secreting tumors
• acute control of bleeding from esophageal varices
What are the side effects of octreotide?
• GI disturbances
• gallstones
• bradycardia, cardiac arrhythmias
• thyroid disruption
What are the clinical applications and side effects of pegvisomant?
• clinical application: acromegaly
• side effects: minimal, liver enzyme increase on induction but not failure
What are the two effects that bromocriptine has?
Dopamine D2 receptor agonist suppresses pituitary secretion of:
- prolactin
- GH
What are the clinical applications of bromocriptine?
• GH based: acromegaly
• prolactin based: hyperprolactinemia
What are the side effects of bromocriptine?
• psychiatric disturbances, confusion
• G.I. disturbances
• orthostatic hypotension
• headache
• vasospasm
What is leuprolide?
• a GnRH analog that increases LH and FSH secretion with intermittent pulsatile administration (used for fertility)
• continuous non-pulsatile administration reduces LH and FSH secretion (endometriosis, precocious puberty, trans medicine)
What is the clinical application of oxytocin?
• induction and augmentation of labor
• control of uterine hemorrhage post delivery
What are the ADH V2 receptor agonist?
Desmopressin and vasopressin
~ used in central diabetes insipidus, hemophilia, and von Willebrand disease (Desmo)
What is the ADH receptor antagonist (V1a and V2 receptors)?
Conivaptan
~ typically used for hyponatremia stabilization in hospitalized patients (infusion only)
What tumors/diseases cause hyperpituitarism?
• adenoma (lactotroph, somatotroph, corticotrophin, gonadotroph)
• carcinoma
• genetics
What pituitary pathology causes hypopituitarism?
• apoplexy
• Sheehan
• empty sella
• hypothalamic
• inflammatory/infectious
• genetic
Mass effect of a pituitary disease typically affects what first?
Visual defects due to proximity of the optic chasm: bilateral temporal hemianopia
Lactotroph adenoma (prolactinoma)
• most common functioning adenoma
• secretes prolactin, stimulates breastmilk production, inhibits ovulation and spermatogenesis
• more commonly seen in women of reproductive years
Somatotroph adenoma
• excessive secretion of growth hormone, stimulation of hepatic secretion of insulin like growth factor-1 (IGF1)
• can cause gigantism, acromegaly, secondary diabetes mellitus
• tx: surgery, somatostatin analog (octreotide)
Corticotroph adenoma
• excess ACTH production leading to adrenal hyper secretion of cortisol, hypercortisolism, and cushing disease
Pituitary gland in Cushing disease
• highly basophilic/chromophobic
• positive ACTH immunohistochemistry
• densely granular EM
• crooke hyaline changes
Gonadotroph adenoma
• secretes hormones inefficiently/not at all (LH, FSH) leading to decrease energy/libido in men and amenorrhea in women from decreased LH
Thyrotroph adenoma
• a very rare, one percent of pituitary adenomas
• can cause hyper thyroidism by excessive TSH release
Non-functioning adenomas typically present with what finding?
Mass effect causing other brain injuries/symptoms. Hypopituitarism which may lead to pituitary apoplexy
What is the defining feature between a micro versus macroadenoma?
Macro is greater than 1 cm
Why does hypopituitarism occur?
• typically due to destructive processes such as tumors, trauma, subarachnoid hemorrhage, surgery, apoplexy, ischemia, TB/sarcoidosis
What is pituitary apoplexy?
• acute hemorrhage into the pituitary, often pre-existing adenoma
• sudden excruciating headache and diplopia, cardiovascular collapse, LOC, and death possible
What is Sheehan syndrome?
• postpartum pituitary necrosis
• anterior pituitary normally doubles and size during pregnancy without an increased blood supply from low pressure venous system (obstetric hemorrhage or shock may lead to infarction due to low blood supply)
• Posterior pituitary uninvolved due to separate arterial blood supply, eventually replaced by fibroid tissue or empty sella
What is primary empty sella syndrome?
• defect of the diaphragma sella allows arachnoid and CSF to herniate into the sella, compressing the pituitary
• most common in women with a history of multiple pregnancies
• results in visual defects, aberrant hyperprolactinemia
What is secondary empty sella syndrome?
• mass such as adenoma is surgically removed or infects lead to loss of function of the pituitary gland
What are the most common hypothalamic lesions?
• benign: craniopharyngioma
• metastatic tumors (breast, lung)
• radiation of other brain or nasopharyngeal areas
What are the common hypothalamic suprasellar tumors?
• gliomas (pilocytic astrocytoma, NF1)
• craniopharyngioma (Rathke pouch remnant)
~ slow growing, children typically have adamantinomatous type, adults have papillary type with calcification
What are the three components of an adamantinomatous type of a craniopharyngioma?
- Palisading epithelium
- Stellate reticulum
- Wet keratin
What are the gene mutations of adamantinomatous type of a craniopharyngioma?
Beta-Catenin and Wnt
What is the appearance of the papillary type of a craniopharyngioma?
Non-keratinizing squamous epithelium and capillary fibrovascular stroma
What is the mutation commonly associated with the papillary type of a craniopharyngioma?
BRAF V600E
What inflammatory/infectious properties can cause pituitary destruction and hypopituitarism?
• sarcoidosis
• tuberculosis
• meningitis
What is a genetic defect that can result in hypopituitarism, a defect of GH, prolactin, and TSH?
mutation of pituitary specific PIT-1 gene
GH deficiency in children causes what?
Pituitary dwarfism
Gonadotropin deficiency causes what?
Amenorrhea, infertility, decreased libido, impotence, loss of pubic and axillary hair
TSH deficiency causes what?
Hypothyroidism
ACTH deficiency causes what?
Hypoadrenalism
MSH (melanocyte stimulating hormone) deficiency results in what?
Color deficiency— pallor
What are the water soluble hormones?
• peptides
• proteins
• glycoproteins
What are the lipid soluble hormones?
• steroids
• thyroid hormone
Peptide hormone synthesis and processing: picture/flow chart/graph
What is unique about peptides/proteins/glycoprotein hormones?
• there are large protein molecules which dissolve well in the blood
• they are broken down quickly by peripheral enzyme systems
• bind surface membrane receptors and cause cellular response through signal transduction systems (secondary messenger systems that are fast, and gene transcription which is slow)
What is unique about lipid soluble hormones (steroids and cholesterol derived, and thyroid hormones)?
• lipophilic and easily cross membranes
• bind carrier proteins in order to travel in the blood, have a longer half-life
• cytoplasmic or nuclear receptors
What is the parent compound for all steroid hormones?
Cholesterol
Where in the body is norepinephrine turned into epinephrine?
In the adrenal medulla
Catecholamines (dopamine, norepinephrine, epinephrine) are _______ soluble
Water— even though they come from Tyrosine (like thyroid hormones that are lipid soluble)
What is a common carrier of steroid/TH hormones in the blood?
Albumin
Steroid hormones act primarily on (intracellular/extracellular) receptors
Intracellular receptors
What receptor is regulated in response to T3?
Beta adrenoreceptors (heart is more sensitive to catecholamines in the presence of thyroid hormone)
What receptor is down regulated with chronic stress?
Growth hormone (GH)
Hormone interactions: synergism, permissiveness, antagonism
Synergism: combined effect > sum of individually effects
Permissiveness: need second hormone to get full effect
Antagonism: one substance opposes the action of another
What are the three tiers of hypothalamic pituitary axis regulation?
- Hypothalamus (brain) releases hormones— GHRH, TRH, CRH, GnRH through portal system
- Pituitary secretes stimulating hormones— GH, TSH, ACTH, LH, FSH
- Peripheral target gland secrete peripheral hormones— IGF, thyroid hormone, cortisol, sex hormones
The secretion of peripheral hormones, causes what effect on the hypothalamus?
Negative feedback
What are the principal steroidogenic organs?
- Adrenal glands
- Gonads (ovaries, testes)
- Placenta
The body synthesizes cholesterol from what?
- De Novo via acetyl-CoA in the endoplasmic reticulum
- Uptake from dietary fat, lipoprotein particle
What are the steroid hormones?
Progesterone (intermediate of all), cortisol, corticosterone, aldosterone, testosterone, estradiol
What protein is required to transport cholesterol from the outer mitochondrial membrane to the mitochondrial matrix?
Steroid acute regulatory protein (StAR)
The rate limiting step in all steroids synthesis is what?
The conversion of cholesterol to pregnenolone by the mitochondrial matrix enzyme P450scc (CYP11A1)
What is Wolman disease?
Inherited mutations in lysosomal acid lipase (LAL). Characterized by cholesterol engorged macrophage infiltration of organs and death by organ failure in infancy
What is congenital lipoid adrenal hyperplasia?
• caused by mutation in StAR. Characterized by steroid hormone insufficiency resulting in female external genitalia and genetic XY individuals, salt wasting, and destruction of tissue due to fat accumulation
Wolman disease, lysosomal acid lipase deficiency, result in what liver findings?
- liver steatosis
- crystals of cholesterol esters in Kupffer cells
What is required to convert cholesterol to pregnonolone?
• CYP450scc (carbons are hydroxylated, bonds cleaved)
• 3 molecules of NADPH
• 3 molecules of oxygen
What part of the adrenal glands are catecholamines synthesized in? Steroids?
Catecholamines: adrenal medulla
Steroids: adrenal cortex
Region of the adrenal gland and its secretions
• determined by gradient of WNT/beta-catenin and cAMP/PKA
What is Addison’s disease?
• loss of adrenal function
• can be caused by TB/autoimmune reaction
• symptoms: fatigue, weight loss, hypotension, nausea, vomiting, hyperpigmentation due to increased ACTH activity in melanocytes
What is the most common cause of congenital adrenal hyperplasia?
Inherited mutations in P450c21 (CYP21) resulting in a less active enzyme (21 hydroxylase)—> this causes pregnonolone and progesterone to divert to androgen production
What are the symptoms of CYP21 mutated congenital adrenal hyperplasia? (21beta-hydroxylase deficiency)
- decreased cortisol—> increased ACTH
- decreased mineralcorticoids—> hypotension, hyponatremia, hyperkalemia
- increased androgens—> early puberty, masculinization infemales
What are the symptoms of CYP17 mutated congenital adrenal hyperplasia? (17alpha-hydroxylase deficiency)
• decreased cortisol—> increased ACTH
• increased mineralocorticoids—> hypertension, hypokalemia
• decreased sex hormones—> XX, XY anatomically female without maturation
What are the symptoms of CYP11 mutated congenital adrenal hyperplasia? (11beta-hydroxylase deficiency)
• decreased cortisol —> increased ACTH
• increased 11 deoxycorticosterone—> hypertension
• increased sex hormones—> masculinization in females
What are the two cell types of the thyroid gland?
- Follicular/principal cells
- Parafollicular/C-cells
What are thyroid follicles?
• structural unit of thyroid
• simple epithelium: cuboidal, squamous, columnar depending on colloid/activate
• colloid contains a thyroglobulin (gel)
Explain the follicular/principal cells
• apical ends of cells adjacent to colloid, microvilli that extends into the colloid
• basal end of cells rest on basement membrane
• slightly basophilic cytoplasm, round nuclei, prominent nuclei
• synthesize thyroid hormones (T3, T4)
What is the difference between an inactive and an active follicular/principal cell?
• inactive: resting, basal level of thyroglobulin, squamous to cuboidal, few mitochondria/small Golgi, some rough ER
• active: stimulated by TSH from pituitary, columnar cells, numerous mitochondria/enlarged Golgi/increased rough ER, lipid droplets and PAS positive, releases T3 and T4 on basal surface
How does the thyroid gland change as it goes from inactive to active?
• lining endothelial cells go from squamous/flat to large columnar filled with colloid
What are parafollicular cells/C-cells?
• occurs singly or in small groups between follicular cells and membrane
• neuroendocrine cells that synthesize calcitonin
What cell is this?
Parafollicular thyroid gland cell
What does calcitonin (released by C-cells) do?
• lowers blood calcium by inhibiting bone resorption
• decreases osteoclast motility/numbers
• promotes excretion of calcium and phosphate from the kidneys
Where is thyroglobulin stored?
In colloid in the thyroid gland (glycoproteins and tyrosine residues available available for iodination—> T3 and T4 precursors)
How is T3/T4 created?
Iodine of thyroglobulin with tyrosine, stimulated by TSH produced by thyrotropes in the pars distalis of the pituitary
• 1tyrosine = monoiodotyrosine
• 2 tyrosine = diiodotyrosine
• 1 MIT + 1 DIT = T3
• 1 DIT + 1 DIT = T4
What are the two pathways for T3 and T4 production after endocytosis?
1. Lysosomal/physiologic: endosomes fuse with lysosomes,T3/T4 is released from Tg, active hormone T2/T4 diffuses through the cell and released at basal surface to capillaries
2. Transepithelial pathway: cell surface receptor megalin binds thyroglobulin and all allows it to skip the lysosome, iodinated thyroglobulin is released at the basal surface
What are the three types of cells of the parathyroid gland?
- Chief/principal cell
- Oxyphil cells
- Fat cells
What are the chief/principal cells of the parathyroid gland?
• small cells, most numerous, slightly acidophilic cytoplasm
• replicate when chronically stimulated by changes in blood calcium levels
• parathyroid hormone, PTH synthesis, storage and secretion to regulate circulating calcium
What is parathyroid hormone, and what does it stimulate?
• a peptide involved in the regulation of calcium and phosphate levels
• it increases blood calcium by stimulating osteoblasts to produce osteoclast stimulating factor (RANKL)—> bone resorption increases blood calcium
What are oxyphil cells of the parathyroid gland?
• larger than chief cells, smaller and dark staining nuclei with no known secretory function
• large eosinophilic cytoplasm that is finally granular due to numerous mitochondria
Where is the parathyroid gland developed from embryologically?
Derived from the pharyngeal endoderm of the the third and fourth pharyngeal pouch
~ principal cells differentiate first to regulate calcium, oxyphil cells differentiate at puberty
What is the pineal gland?
• a small pinecone shaped body with a Pia matter capsule attached by a stalk to the roof of third ventricle between the two hemispheres of the brain
• contains pinealocytes and interstitial (glial) cells
What are pinealocytes?
• majority (95%) of pineal gland cells
• resemble neuroendocrine cells
• produce melatonin at night
What are the interstitial (glial) cells of the pineal gland?
• Astrocytes (supportive role) similar to the pituicytes of the posterior pituitary
What is brain sand (corpora arenacea)?
• an area of the pineal gland that has concentrations of calcium phosphate and carbonate on carrier proteins
• accumulates with age, no known function
• use as a radiological marker because it is opaque on x-rays
Low light signals from the eye, induce what in the pineal gland?
Increase melatonin, reduced GnRH and GnIH, therefore reduced FSH, reduced LH
What alters emotional responses to changes in day length (seasonal effective disorder, Jetlag leg)?
The pineal gland
What is thyrotoxicosis?
Hyperthyroidism, a hypermetabolic state caused by excess circulating T3 and T4
• primary: excess production by the thyroid gland (most common)
• secondary: extrathyroid source
What is the most useful screening test for hyperthyroidism/thyrotoxicosis?
TSH level (will be low)
What are the three most common causes of hyperthyroidism?
- Diffuse hyperplasia, Graves’ disease
- Multinodular goiter
- Hyperfunctional adenoma
What are the clinical features of hyperthyroidism?
• hypermetabolic and increased sympathetic tone: warm, flushed skin, heat intolerance, increase sweating, weight loss despite increased appetite
• cardiac manifestations: increased cardiac contractility, tachycardia, palpitations, cardiomegaly, a fib, left ventricular dysfunction
What is Graves’ disease?
- most common cause of endogenous hyperthyroidism: triad of thyroid toxicosis, ophthalmopathy, dermatopathy
- autoimmune, secondary hypersensitivity reaction
- glycosaminoglycan deposition in the ECM and lymphoid infiltrates
- lab findings: high serum free T3/T4 and low TSH
Understanding thyroid function test: primary, secondary, hyperthyroidism, and T3 thyrotoxicosis
What are the treatments for Graves’ disease?
- propylthiouracil: decrease synthesis of thyroid hormone (blocks T 4 5’ deiodinase)
- radioiodine ablation
- surgery for large goiters compressing adjacent structures
What is a goiter?
Thyroid enlargement and impaired synthesis of thyroid hormone, usually due to dietary iodine deficiency. Results in compensatory increase in TSH, causing hyperplasia and hypertrophy of follicular cells and gross enlargement of the gland
Where are goiters seen most commonly?
• endemic- where soil, food, water have low iodine
• sporadic- female predominance, puberty/young adults, unclear cause
What is hypothyroidism?
• decrease production of thyroid hormone, increased with age, more common in females
• primary: defect and thyroid gland (congenital, auto immune, iatrogenic)
• secondary: defect elsewhere in the axis (division of TSH, TRH)
What is congenital hypothyroidism?
- hypothyroidism and infancy/early childhood typically in areas endemic of iodine deficiency, maternal hypothyroidism, agenesis, or dishormonogenic goiter
- impaired skeletal and CNS development, short stature, coarse facial features, mental deficiency
Hypothyroidism in older children/adults is what?
Myxedema— general slowness, decreased metabolic rate. Caused by iodine deficiency, drugs (lithium), or thyroiditis
~ measuring TSH is the most sensitive screening test
Hashimoto thyroiditis:
• most common cause of hypothyroidism where iodine levels are sufficient
• autoimmune (autoantibodies to thyroglobulin and thyroid peroxidase) characterized by progressive gland destruction, Hurthle cell change, mononuclear infiltrates with germinal centers with or without fibrosis
What is subacute lymphocytic thyroiditis?
• painless, postpartum thyroiditis presenting with mild hyperthyroidism, goiter, or both
• autoimmune, circulating anti-thyroid peroxidase antibodies
• no hurthle cell metaplasia, otherwise similar to Hashimoto’s
What is subacute Granulomatous thyroiditis (De Quervain)?
• painful, age 40-50, women
• triggered by viral infection, Coxsackie, mumps, measles, adenovirus
• most common cause of thyroid pain, transient hyperthyroidism (high T3, T4 and low TSH) that is self limiting and normal function returns in 6-8 weeks
What is Riedel fibrosing thyroiditis- Woody thyroid?
• rare, fibrous disease causing thyroid gland hardening
• IgG4 related systemic disease
• clinical features: hard, immovable thyroid mass, hypothyroidism, compression effect (difficulty swallowing, breathing, voice changes)
What is a follicular adenoma (thyroid neoplasia)?
• discrete encapsulated solitary masses of follicular epithelium, typically non-functional
• GOF mutation in TSHR, GNAS
• rare: RAS or PIK3C a mutations or a PAX8-PPARG fusion gene
What does a thyroid follicular adenoma look like morphologically?
• gray/white two red/brown cut surface
• hemorrhage, fibrosis, calcification seen
• uniform small follicles with some colloid, follicle cell monotony, mitotic figures are rare
Microscopic examination for what must be done to exclude carcinoma when looking at thyroid adenoma?
Entire tumor capsule must be examined because capsular and vascular invasion define carcinoma
What does the Hurthle cell type look like in the transition from traditional cells in follicular adenoma?
What are the types of thyroid carcinoma?
• papillary, most common
• follicular
• anaplastic
• medullary
~ mutations in RET gene, or MEN2 are common genetic predispositions
Follicular thyroid carcinoma genetic mutation:
• women, 40-60
• acquired mutations that activate RAS or the PI3K/AKT arm of the receptor tyrosine kinase pathway (or LOF of PTEN)
Follicular thyroid carcinoma morphology
• gross: single nodule, gray to pink/tan to yellow with hemorrhage/necrosis occasionally
• microscopic: uniform cells forming small molecules, less colloid than normal, Hurthle variant occurs
What is the typical treatment of follicular thyroid carcinoma?
Although slowly enlarging painless mass, total thyroidectomy followed by radioactive iodine and thyroid hormone treatment to suppress endogenous TSH is the treatment
Papillary thyroid carcinoma gene mutations:
- most common thyroid malignancy, 25-50 years old or childhood
- exposure to ionizing radiation is a risk factor
- GOF mutation of RET or NTRK1 receptor tyrosine kinase or BRAF
What does papillary thyroid carcinoma look like morphologically?
• gross: solitary/multifocal, cystic, fibrosis, calcification, papillae sometimes visible on surface
• microscopic: branching Papillae with fibrovascular core, clear ground glass nuclear appearance (orphan Annie eye), calcified psammoma bodies
What are the variant papillary thyroid carcinomas?
• Tall cell: older individuals, vascular invasion, BRAF, PTC/RET translocation
• diffuse sclerosing: younger age, papillary growth, squamous nest simulating Hashimoto, lymph involvement
• follicular variant: nuclear features of PTC but follicular architecture (can be infiltrative or encapsulated)
Anaplastic thyroid carcinoma gene mutations
• rare, high mortality undifferentiated tumor of thyroid epithelium, around 65
• RAS, PIK3CA mutations as well as TP53 in activation or activating beta-catenin
Medullary thyroid carcinoma:
• neuroendocrine neoplasm derived from parafollicular C- cells
• excessive secretion of calcitonin (occasionally also serotonin, ACTH, VIP) which can lead to neck masses/dysphasia/hoarseness, diarrhea (VIP), and Cushing (ACTH)