[OPTIONAL] Endocrinology Review Flashcards
Which endocrine hormones utilize the PLC mechanism? (GOAT HAG mnemonic)
GnRH + Oxytocin + ADH + TRH + Histamine + Angiotensin II + GHRH
GOAT HAG
Which enzyme is responsible for the degradation of intracellular cAMP to inactive 5’ AMP in the adenylyl cyclase/cAMP pathway?
Phosphodiesterase
What are the 2 classes of homrones which are amines?
- Catecholamines (epinephrine, NE, and dopamine)
- Thyroid hormones
When a steroid hormone binds its receptor what occurs to the hormone-receptor complex?
Dimerizes and binds via zinc fingers to specific DNA sequences, called steroid-responsive elements (SREs)
Once the steroid hormone-receptor complex dimerizes and binds to the SREs of the target gene, what has this complex now become and what does it regulate?
A transcription factor that regulates the rate of gene transcription
What is the epithelial and neural portion of the pituitary gland?
- Anterior pituitary (adenohypophysis) = epithelial portion
- Posterior pituitary (neurohypophysis) = neural portion
Generally cancers of the pituitary expand where and compress what?
Up into the brain and compress the optic nerves
The posterior pituitary is a collection of axons whose cell bodies are located in the hypothalamus; what are these 2 cell bodies and which neuropeptides is each cell body associated with?
- Supraoptic nucleus (SON) –> mainly ADH
- Paraventricular nucleus (PVN) –> mainly oxytocin
Which 6 hormones are secreted by the anterior pituitary?
- FSH
- LH
- ACTH
- TSH
- Prolactin
- GH
*FLAT PiG*
How is the anterior pituitary connected to the hypothalamus?
Hypothalamic-hypophysial portal vessels
Which portion of the pituitary gland has both neural and endocrine connections with the hypothalamus; which has exclusively neural?
- Anterior pituitary = BOTH endocrine and neural
- Posterior pituitary = only neural
Contrast primary endocrine disorder, secondary endocrine disorder, and tertiary endocrine disorder.
- 1° disorder = due to defect in the peripheral endocrine gland
- 2° disorder = due to defect in the pituitary gland
- 3° disorder = due to defect in the hypothalamus
Gonadotrophs release what hormone(s)?
FSH and LH
Somatotrophs release what hormone?
GH
What is the most important somatomedin mediating the indirect effects of GH?
IGF-1
What is the effect of GH on insulin, blood glucose levels, and adipose tissues?
- Causes insulin resistance –> ↑ blood insulin
- Effects are diabetogenic –> ↑ in blood glucose levels
- ↑ lipolysis in adipose tissue
What are 2 metabolic effects of GH which are mediated by somatomedins (IGF-1)?
- ↑ protein synthesis and organ growth (↑uptake of AA’s)
- ↑ linear growth (↑ metabolism in cartilage-forming cells and chondrocytes proliferation)
What are 2 of the most potent stimuli for GH secretion?
Hypoglycemia and starvation
Conditions with excess secretion of GH are treated with what?
Somatostatin analogs –> ocreotide
What are 4 ways that GH deficiency can result?
- ↓ secretion of GHRH (hypothalamic dysf.)
- ↓ GH secretion (pituitary dysf.)
- Failure to generate somatomedins in the liver
- GH or somatomedin resistance (deficiency of receptors)
GH excess causes what if before puberty or what if after puberty?
- Before puberty = gigantism
- After puberty = acromegaly
Where does prolactin released from the anterior pituitary act and what is its function?
Acts on the hypothalamus to ↓ GnRH secretion —-> ↓ FSH and LH
What is the inhibitory and stimulatory pathway from the hypothalamus regulating prolactin release from the anterior pituitary?
- Inhibitory = Dopamine (aka PIF)
- Stimulatory = TRH
How does prolactin inhibit its own secretion?
By increasing the synthesis and secretion of dopamine from the hypothalamus (negative feedback)
What are the 2 most important stimuli for prolactin secretion?
- Breast feeding
- Pregnancy
Secretion of ADH is most sensitive to changes in what?
Plasma osmolarity
What are 6 triggers for the secretion of ADH from the posterior pituitary?
- ↑ plasma osmolarity = most important stimulus
- ↓ BP
- ↓ blood volume
- ↑ Angiotensin II
- Sympathetic stimulation
- Dehydration
In volume expansion (aka hypervolemia) what occurs with ADH secretion even in the presence of increased plasma osmolarity?
ADH secretion is inhibited
What is the major action of ADH and via what receptor?
- ↑ water permeability of principal cells in the late distal tubule and collecting duct
- Via the V2 receptor on principal cells
What is the effect of ADH on vascular smooth muscle and via which receptor?
Contraction of vascular smooth m. (aka vasoconstriction) via the V1 receptor
Central diabetes insipidus is caused by what; what are ADH levels like?
- Caused by: damage to posterior pituitary or destruction of hypothalamus
- LACK of ADH so will see ↓ plasma ADH
What will be seen in terms of urine production and serum osmolarity in patient with central DI?
- Large volumes of dilute urine
- Bodily fluids are concentrated i.e., ↑ serum osmolarity and ↑ serum [Na+]
What is occuring in nephrogenic DI; what are plasma levels of ADH like?
Kidneys are unable to respond to ADH (↑ plasma ADH)
What are 2 major causes of nephrogenic DI?
- Drugs like lithium
- Chronic disorders i.e., polycystic kidney disease, sickle cell anemia
What is the Tx of Central DI vs. Nephrogenic DI?
- Central DI is treated with desmopressin (ADH analogue)
- Nephrogenic DI is treated with thiazide diuretics (desmopressin does NOT work)
What is the serum and urine osmolarity like in SIADH?
- Serum osmolarity is decreased due to excess water reabsorption by collecting ducts —> HYPOosmolarity fails to inhibit ADH release
- Urine is inappropriately concentrated (i.e., too concentrated for the serum osmolarity)
What are the 3 layers of the adrenal cortex and what are the main hormones produced by each layer?
- Zona Glomerulosa –> mineralocorticoids (aldosterone)
- Zona Fasciculata –> glucocorticoids (cortisol)
- Zona Reticularis –> androgens (DHEA)
Which hormones are produced by the adrenal medulla?
Catecholamines (epinephrine and NE)
What is the precursor for all adrenal cortex hormones?
Cholesterol
Which pathway(s) of hormone synthesis in the adrenal cortex does the enzyme 17α-hydroxylase play a role in?
- Cortisol synthesis
- Androgen synthesis
Which pathway(s) of hormone synthesis in the adrenal cortex does the enzyme 21β-hydroxylase play a role in?
- Aldosterone synthesis
- Cortisol synthesis
Which pathway(s) of hormone synthesis in the adrenal cortex does the enzyme 11β-hydroxylase play a role in?
- Aldosterone synthesis
- Cortisol synthesis
For each indicate if the levels will be ↑ or ↓ in 17α-hydroxylase deficiency: mineralocorticoids, cortisol, sex hormones, BP, and [K+]
- ↑ mineralocorticoids
- ↓ cortisol
- ↓ sex hormones
- ↑ BP
- ↓ [K+]
Which enzyme deficiency is associated with ↓ androstenedione levels?
17α-hydroxylase