Pituitary Patho Flashcards
Why are steroid hormones able to cross cell membranes
They contain cholesterol making them fat soluable
What are the three classes of hormones
Peptide and protein, steriod, and Amine
what are the secondary messenger systems of protein hormones
Adenylate Cyclase Mechanism,Phospholipid Mechanism, Guanylate Cyclase Mechanism, Tyrosine Kinase Mechanism
What type of steriod hormones do the following produce
Adrenal Cortex
Testes
Ovaries
Corpus Luteum
Placenta
Kidney
Adrenal Cortex= Cortisol, Aldosterone, Androgens
Testes=Testosterone
Ovaries= Estrogens, Progesterone
Corpus Luteum= Estrogens, Progesterone
Placenta= Estrogens, Progesterone
Kidney= 1,25-Dihydroxycholecalciferol
what are the 2 pathways of the synythesis of Amine hormones from tyrosine
1) Tyrosine to Dopamine to NE to Epi
2) Tyrosine to Thyroid hormone
Why does the SNS release NE instead of Epi
the SNS lacks the enzymes(phenylethanolamine-N-methyltransferase) to make epi from NE
What type of amine hormones do the following tissues produce
Hypothalamus
Thyroid
Adrenal medulla
Hypothalamus= Dopaine
Thyroid= T3, T4
Adrenal medulla= NE, epi
how does dopamine act as a hormone
it inhibits Prolactin
what 3 things may occur to Free hormone after it is released from endocrine cells? when does it have biological effects?
1) Carrier-bound hormone
2) hormone receptor (bio effects)
3) Hormone degradation
what factor has the largest effect on hormone half-life
Those that are protein bound have longer half lives (days compared to min)
what is the formula for metabolic clearance rate of hormones
MCR = (mg/minute removed) / (mg/ml of plasma) = ml cleared/minute
what are the 6 hormones produced in the anterior pituitary
GHRH:
GIH (Somatostatin)
CRH:
TRH:
GnRH:
PIF (dopamine)
why does inc ACTH cause inc pigmentation
inc ACTH= inc MSH(melanocyte stimulating hormone)
what hormones would be affected by a clot in the pituitary? Why?
All of those released by the Ant pit because the ant pit is stimulated by vascular connections whereas the post pit only has neuro connections
what is the adenohypophysis
ant lobe of the pituitary
how does the post pituitary maintain BP
PVN responds to inc osmolarity by inc action potentials= inc ADH release
what local mass effects can result from hyperpit
Optic chiasm-
ICP
Hemorrhage into an adenoma resulting in rapid enlargement of lesion-pituitary apoplexy
what type of vision loss will occur from pituitary compression of the optic chiasm
bitemporal hemiopsia
what can cause hypopit
Result of various destructive processes including ischemia, radiation, inflammation and non-functioning neoplasms.
what is the most common cause of hyperpit
pituitary adenoma
which type of pit tumors of often more progressed when found(secretory or non-secretory)
secretory are often found earlier because they produce Sx from excess of hormone
what the sizes of micro and macroadenomas of pituitary
micro=<1cm
macro =>1cm
how are genetic abnormalities in G-protein(alpha, beta, gamma) associated with pituitary adenomas
activation of G-protein increases cAMP which is a mitogenic stimuli promoting cellular proliferation and hormone synthesis
what is a GNAS gene mutation
It incodes for the Alpha subunit of the G protein
40% of somatotroph cell adenomas have GNAS mutations
what is a inherited mutation leading to hyperpit tumors
mutation in tumor suppressor gene
what is the most common functional pituitary tumor
prolactinoma (lactotroph adenoma)
how large of a prolactinoma is required before Sx are produced
Prolactin secretion is extremely efficient; a microscopic adenoma can produce enough prolactin to produce symptoms.
what occurs after prolactinomas undergo dystrophic calcification
pituitary stone formation
what determines the amount of prolactin production from a prolactinoma
Prolactin production is proportional to tumor size.
what inhibits prolactin production. When may this occur?
dopamine
1-interruption of dopamine due to head injury
2-drugs (psychotropics)
what are the hormone effects of hyperprolactinemia. What population is it easiest to detect in?
Amenorrhea
Galactorrhea
Loss of libido
Infertility
Becasue of the Sx it is easier to detect in females 20-40yo
what mass effects may prolactinomas produce
Headache
Fatigue
Neck pain
Seizures
Visual field effects
what is the Tx for prolactinomas
Medications Bromocriptine: Dopamine agonist
Surgery
Radiation
what other hormone effects are likely to occur with prolactinomas
dec TSH= hypothyroidism
dec cortisol= addisons
dec FSH= dec fertility
what is the pathophys mechanism from somatotroph adenomas
Hypersecretion of GH stimulates hepatic secretion of insulin-like growth factors (IGF-1)which cause the clinical manifestations of this disorder.
what occurs if excess GH prior to bone maturity
excess GH results in gigantism: generalized increase in body size & long limbs
what occurs if excess GH post bone maturity
Acromegaly: Enlargement of the head, hands, feet, jaw (prognathism), tongue and soft tissues
what other effects does GH cause besides musculoskeletal
Excess GH results in diabetes and accelerated atherosclerotic cardiovascular disease as well as other end organ effects from HTN.
what is the pathophys mechanism of corticotroph adenomas
Excess production of corticotrophin ((ACTH) = Increased cortisol production hypercortisolism (Cushing syndrome)
what s/sx are common with cushings
- fat/ water retention causing moon face, buffalo hump, trunkal obesity, striae
- DM2 (cortisol causes insulin resistance)
- infertility(dec FSH/LH)
- dec growth (dec GH)
- hypothyroid (dec TSH
how much parenchyma is usually lost before hypopit s/sx occur
75%
what is Sheehan syndrome
inc blood during preg so vessles become accustomed to lareg volume. Rapid hemorrhage causes vasospasm and death of ant pit. Usually dont see s/sx until months later
what is panhypopituitarism
all hormones are deficient
what is primary empty sellas syndrome
due to a defect in the diaphragma sellae or increased ICP allowing the encroachment of arachnoid and CSF into the sella and compressing the gland.
what is secondary empty sella syndrome
due to intervention for a pituitary process usually adenoma which results in the destruction/removal
what results from posterior hypopit
dec oxytocin
dec adh= diabetes insipidis
what results from ADH excess? What can cause this?
SIADH
1-Ectopic production
2-Infection of the pituitary
3-Medications
4-inc ICP
what Sx result from 130-140 Na
Anorexia, fatigue and dyspnea
what Sx result from 120-130 Na
Nausea
Vomiting
Abdominal cramping
what Sx result from 110-115 Na
Confusion
Lethargy
Muscle twitching
Convulsions
