Endocrine Flashcards
Where does the thyroid gland develop?
thyroid diverticulum arises from floor of primitive pharynx, descending into neck. It is connected to tongue by thyroglossal duct which norally disappears but may persist as pyramidal lobe of thyroid.
What is the normal remnant of the thyroglossal duct?
foramen cecum
What is the most common site of ectopic thyroid tissue?
tongue - lingual thyroid
How does a thyroglossal duct look like?
an anterior midline neck mass that MOVES w/ swallowing. Make sure you remove it b/c it can get infected
Tell me about the fetal adrenal gland?
- consists of an outer adult zone and inner active fetal zone.
- Adult zone is dormant during early fetal life but begins to secrete cortisol late in gestation.
- Cortisol secretion is controlled by ACTH and CRH from fetal pituitary and placenta.
Why is cortisol necessary for the fetus?
- responsible for fetal lung maturation and surfactant production
What is the embryonic derivative of the adrenal cortex and medullar?
- cortex = mesdoerm
- medulla = neural crest
What is produced in the adrenal medulla?
it’s stimulated by pregangionlic sympathetic fibers to make catecholamines via chromaffin cells
What is produces in the adrenal cortex?
- Renin-Angiotensin activates Zone Glomerulosa to make Aldosterone
- ACTH, hypothalamic CRH stimulates Zone Fasciculata to make cortisol and some sex hormone
- ACTH, hypothalamic CRH stimulates Zona Reticularis to make sex hormones
How do the adrenal glands drain?
- Left adrenal –> left adrenal vein – > left renal vein –> IVC
- Right adrenal –> right adrenal vein –> IVC
What is the most common tumor of the adrenal medullar for an adult?
pheochromcytoma
What is the most common tumor of the adrenal medulla in kids?
neuroblastoma
What is stored in the posterior pituitary? (neurohypophysis)
- secretes ADH and oxytocin
- remember derived from neuroectoderm
What is released from the anterior pituitary? (adenohypophysis)
Secretes FSH, LH, ACTH, TSH, prolactin, GH, MSH
- Remember derived from oral ectoderm (Rathke’s pouch)
There are some hormones who have alpha and beta subunits. What are they and what is the importance of the subunits?
- FSH, LH, TSH, bhCG
- all the alpha subunits are the same
- the Beta subunits determines hormone specificity
What are the acidophilic hormones?
GH, prolactin
What are the basophilic hormones?
FSH, LH, ACTH, TSH
What makes up the endocrine pancreas?
- alpha cells- make glucagon
- beta cells- make insulin
- delta cells- make somatostatin
- islets of langerhans are made up of peripheral alpha cells w/ central beta cells and interspersed delta cells
What are all the hormones involved in the HP and HPA axis?
- TRH –> TSH and prolactin
- Dopamine inhibits prolactin
- CRH –> ACTH, MSH, beta-endorphin
- GHRH –> GH
- Somatostatin inhibits GH, TSH
- GnRH –> FSH, LH
- Prolactin inhibits GnRH
What is the precursor molecule for ACTH?
-POMC which also contains sequences for other hormonal peptides. eg MSH and beta-endorphin
Where is somatostatin made?
throughout the GI Tract notably by delta cells in pancreas and GI mucosa
- also made by nervous system
What effect do somatostatin have?
- decrease endocrine and exocrine secretions
- decrease splanchnic blood flow
- decrease GI motility and gallbladder contraction
What are the clinical uses of somatostatin? eg octreotide
- pituitary excess - acromegaly, thyroitropinoma, ACTH secreting tumor
- GI endocrine excess: ZE syndrome, carcinoid syndrome, VIPoma, glucagonoma, insulinoma
- Need to decrease splanchnic circulation : portal HTN and bleeding peptic ulcers, esophageal varicies
What is the function of prolactin?
- stimulates milk production in breast
2. inhibits ovulation in females and spermatogenesis in males by inhibiting GnRH synthesis and release
How is prolactin regulated?
- tonically inhibited by dopamine
- prolactin in turn inhibits its own secretion by increasing dopamine synthesis and secretion
- TRH increases prolactin secretion
What can be used to treat prolactinomas?
dopamine agonists - bromocriptine b/c they inhibit prolactin secretion
What can stimulate prolactin secretion?
Dopamine antagonists - most antipsychotics; and estrogens (OCPs, pregnancy)
What happens to females and males when they have hyperprolactinemia?
- Premenopausal W - hypogonadism, infertility, oligo/amenorrhea, rarely galactorrhea
- Postmenopausal W - non since they are already hypogonadal
- Male - hypogonadism (low T) = decreased libido, impotence, infertility, gynecomastia, rarely galactorrhea
What is the function of GH?
Stimulates linear growth and muscle mass through IGF1/somatomedian secretion. Increases insulin resistance (diabetogenic)
How is GH regulated?
- Released in pulses in response to GHRH
- secretion increases during exercise and sleep
- Secretion inhibited glucose and somatostatin
What are all the steps to make aldosterone?
Cholesterol to Pregnenolone (Desmolase) Preg to Progesterone (3BHSDH) Prog to 11DOC (21hydroxylase) 11DOC to corticosterone (11Bhydroxylase) Corticosterone to Also (Aldo synthase)
What are the steps to make Corisol?
Cholesterol to Preg (desmolase)
- essentially you NEED 17 alpha hydroxylase and 3BHSDH to make 17hydroxyprogresterone
- 17 hydroxyprog to 11deoxycortisol (21OHlase)
- 11 deoxycortisol to cortisol (11BOHlase)
What are the steps to make Testosterone?
need 17 hydryoxylase and 3Bhydroxysteroid DH
- to get to DHT you need 5 Alpha reductase
- Use aromatase to make Estrone and estradiol
What happens w/ a 17 alpha hydroxylase deficiency?
- increased mineralcorticoids
- HTN, hypokalemia
XY - decreased DHT = pseudohermaphroditism (variable, ambiguous genitalia, undescended testes)
XX - externally phenotypic female w/ normal internal sex organs, lacks primary sex characteristics
What happens w/ a 21 hydroxylase deficiency?
- increased sex hormones
- hypotension, hyperkalemia, increased renin activity, volume depletion
- masculinization leading to pseudohermaphroditism in females
What happens w/ a 11 B hydroxylase deficiency?
- increased sex hormones
- decreased aldosterone
- increased 11 DOC
HTN and masculinization
What are all of the congenital bilateral adrenal hyperplasia characterized by?
enlargement of BOTH adrenal glands due to increased ACTH stimulation b/c of decreased cortisol
What are all the functions of cortisol?
- Maintains blood pressure - upregulates alpha1 receptors and increases sensitivity to NE and E
- decreases bone formation
- Anti-inflammatory/immunosuppresives
- Increases insulin resistance (diabetogenic)
- Increases gluconeogenesis, lipolysis, proteolysis - catabolic hormone
- inhibits fibroblasts (causes striae) - decreases collagen synthesis
What are all the anti-inflammatory/immunosuppresive effects of cortisol?
- inhibits production of LT and PGs
- inhibits leukocyte adhesion –> neutrophilia
- blocks histamine release from mast cells
- reduces esoinophils
- blocks IL 2 production
How is cortisol regulated?
- CRH stimulates ACTH causing cortisol production in adrenal zona fasciculata.
- excess cortisol decreases CRH, ACTH, and cortisol secretion
What are the side effects for excess cortisol?
- thinning of skin
- easy bruisability
- osteoporosis
- adrenal cortical atrophy
- peptic ulcers
- diabetes
- immunosuppression
What are the effects of stress?
- gluconeogenesis
- increased lipolysis - increased FFA
- immunosuppression
- higher cortisol levels, more catecholamines
- affects water absorption
- proteolysis = poor muscle tone
- more frequent bowel movements
- viscous secretions
- Sympathetics!!!!
What hormones use the Gs pathway?
FSH, LH, ACTH, TSH, CRH, hCG, ADH (v2), MSH, PTH, calcitonin, GHRH, glucagon
- FLAT ChAMP
What hormones use the cGMP pathway?
NO and ANP
What hormones use the IP3 pathway?
GnRH, GHRH, oxytocin, ADH (V1), TRH, Angiotensin II, gastrin
- GGOAT
What hormones use steroid receptors?
Vit D, Estrogen, T, T3/T4, Cortisol, Aldosterone, Progesterone
What hormones use the intrinsic tyrosine kinase receptor?
Insulin, IGF1, FGF, PDGF, EGF
What hormones use the receptor associated tyrosine kinase?
Prolactin, Immunomodulators (eg cytokines IL2/6/8)
What is the signaling pathway of steroid hormones?
Steroid hormones are lipophilic and therefore must circulate bound to specific binding globulins which increase their solubility.
What happens to T when SHBG increases in men?
lowers free T
What happens to W when SHBG decreases?
raises free T leading to hirsutism
What happens to SHBG during pregnancy?
increases
What is the hormone responsible for controlling the body’s metabolic rate?
TH
What is the source of TH?
follicles of thyroid. Most T3 formed in target tissues
What is the function of TH?
- bone growth (synergism w/ GH)
- CNS maturation
- INcrease B1 receeptors in heart = increased CO, HR, SV, contractility
- Increased basal metabolic rate via Increased NaKAPTase activity = increases O2 consumption, RR, Body temp
- Increased glycogenolysis, gluconeogenesis, and lipolysis
What regulates TH?
TRH stimulates TSH which stimulates follicular cells.
- negative feedback by free T3 to anterior pituitary decreases sensitivity to TRH
- Thyroid stimulating Igs (TSIs) like TSH stimulates follicular cells – Grave’s
What is the Wolff-Chaikoff effect?
excess Iodine temporarily inhibits thyroid peroxidase = decreases iodine organification = decreases T3/T4 production
What happens to TBG in hepatic failure? in pregnancy?
- failure = decreased so decrease in total TH
- pregnancy = increased so increase in total TH
- OCP = increases TBG
What is better T4 or T3?
T4 is the major thyroid product but it’s converted to T3 in peripheral tissues by 5’deiodinase.
- T3 binds receptors w/ greater affinity
What are the steps to make TH?
- I` is taken into follicular cells and oxidized via peroxidase
- Then I2 is added to Thyroglobulin to form MIT and DIT = organification (also done by peroxidase), Y residues are added
- T3/T4 is stored in colloid of thyroid gland
- Follicular cells proteolyze T3/T4 before sending it out into the blood
What inhibits the initial uptake of I` into the follicular cells?
anions - perchlorate, pertechnetate
What inhibits the organification of TH?
antithyroid drugs - PTU, methimazole
What is Cushing’s Syndrome?
increased cortisol due to many reasons
What is the most common cause of Cushing’s syndrome?
exogenous steroids = decreased ACTH, both adrenal glands are atrophic
What are some endogenous causes of Cushing’s Syndrome?
- Cushing’s Disease (75%)
- Ectopic ACTH (15%)
- Adrenal (15%)
What is Cushing’s disease?
due to ACTH secretion from pituitary adenoma. Slight increase in ACTH
- both adrenals will be big
What are causes of ecotopic ACTH?
small cell lung cancer, bronchial carcinoids
- high levels of ACTH
What are causes of adrenal Cushings?
adenoma, carcinoma, nodular adrenal hyperplasia (one adrenal is big, other is atrophic)
- here you have decreased ACTH
What are the clinical findings for Cushing’s syndrome?
- HTN
- WT gain
- Moon facies
- Truncal obesity
- buffalo hump
- hyperglycemia
- skin changes (thinning, striae)
- osteoporosis
- amenorrhea
- immune suppression
How is the dexamethasone suppression test used to ID cushing’s syndrome?
- Normal - should have suppressed levels of cortisol at high and low doses
- ACTH pituitary tumor - will only be suppressed at high doses
- Ecotopic ACTH Tumor and Adrenal producing cortisol tumor - both will have elevated levels of cortisol even at high and low doses of dexamethasone
What is primary hyperaldosteronism?
Caused by adrenal hyperplasia or an Aldosterone secreting adrenal adenoma (Conn) - may be bilateral of unilateral
What are the clinical presentations of primary hyperaldosteronism?
- HTN
- Hypokalemia
- metabolic alkalosis
- Low plasma renin
What is the treatment for a primary hyperaoldosteronism?
Surgery to remove tumor and spironolactone (K sparing diuretic that works by acting as an Aldo antagonist)
What is secondary hyperaldosteronism?
- renal perception of low IV volume results in overactive RAAS
- due to renal artery stenosis, chronic renal failure, CHF, cirrhois, or nephrotic syndrome
- HIGH PLASMA RENIN
What is Addison’s Disease?
Chronic primary adrenal insufficiency due to adrenal atrophy or destruction of disease
- deficiency of aldo and cortisol
What are the clinical findings of Addison’s Dz?
- hypotension (hyponatremic volume contraction)
- hyperkalemia
- acidosis
- skin hyperpigmentation (due to increased MSH from ACTH)
What happens in secondary adrenal insuffiency?
- problem is at the pituitary
- no hyperpigmentation or hyperkalemia
- low cortisol b/c of low ACTH
What happens in tertiary adrenal insufficiency?
abrupt withdrawal of exogenous steroids
- mild HTN
What is Waterhouse Friderichsen syndrome?
Acute primary adrenal insufficiency due to adrenal hemorrhage associated w/ Neisseria meningitidis
What are symptoms of Waterhouse Friderichsen syndrome?
septicemia, DIC, endotoxic shock, petechial rash
What is pheochromocytoma?
Secretes E, NE, and dopamine which can cause episodic HTN
How can a pheochromocytoma be Dxed?
- Urinary VMA, metanephrine, HVA
- plasma catecholamines are elevated
what else is pheochromocytoma associated with?
- neurofibromatosis type 1
- MEN 2A and 2B
What is the treatment for Pheochromocytoma?
remove tumor only after effective alpha and beta blockers is achieved.
- irreversible alpha antagonists must be given first to avoid a hypertensive crisis
- Beta blockers are then given to slow the heart rate
What are the symptoms of a pheochromocytoma?
- High BP
- Pain (headache)
- Perspiration
- Palpitations
- Pallor
What is the rule of 10’s for pheochromocytoma?
10% malignant 10% bilateral 10% extra-adrenal -- bladder 10% calcify 10% kids