Fomina's Hormone Biochemistry

Front 1

Give a few examples of water insoluble lipophilic hormones.

Back 1

Steroids, amines (thyroxin, triiodothyronine), FA derivatives (eicosanoids), Vitamin D

Front 2

Where are lipophilic hormones stores within a cell?

Back 2

They are not stored; they are constitutively synthesized and released.

Front 3

What do lipophilic hormones bind to in plasma and what affect does this binding have?

Back 3

Specific plasma carrier proteins.
Binding increases their solubility, life span, and stabilizes concentration of free hormone.

Front 4

Where to lipophilic hormones bind on their target cells?

Back 4

To intracellular receptors.

Front 5

Give a few examples of hydrophilic hormones.

Back 5

Amines (dopamine, epi, NE), peptides (oxytocin, ADH), proteins (GH, insulin), glycoproteins (FSH, TSH).

Front 6

Where are hydrophilic hormones stored inside the cell?

Back 6

In secretory granules usually.

Front 7

Where do hydrophilic hormones bind on their target cell?

Back 7

Membrane receptors.

Front 8

Where are steroid hormones synthesized?

Back 8

In the adrenal gland, testes, ovaries, placenta, and adipose tissue.

Front 9

Where and from what are steroid hormones synthesized?

Back 9

In the intermembrane space of the mitochondria from cholesterol.

Front 10

How is cholesterol made?

Back 10

From acetate, cholesterol ester stores in intracellular lipid droplets, or from uptake of cholesterol-containing low density lipoproteins (LDLs).

Front 11

Breakdown steroid biosynthesis.

Back 11

Cholesterol is converted to pregnenolone via CYP11A1. Through multiple oxidative enzymatic tranformations, pregnenolone can be converted into:
Glucocorticoids (cortisol)
Mineralocorticoids (aldosterones)
Androgens
Estrogens
Progestins
(Thus inactive--> active)

Front 12

Where is pregnenolone in a cell?

Back 12

Pregnenolone moves between the mit and the ER.

Front 13

Is cholesterol hydrophilic or hydrophobic?

Back 13

Both; cholesterol is amphipathic and thus can easily cross the cell membrane.

Front 14

Is Vitamin D2 hyprophilic or lipophilic? Vitamin D3?

Back 14

They are both lipophilic.

Front 15

How are Vit D2 and D3 activated?

Back 15

Both must undergo dihydroxylation (one hydroxylation in the liver, the second in the kidney)

Front 16

How are Vit D2 and VitD3 obtained?

Back 16

Vit D2: dietary uptake.
Vit D3: synthesized in skin from cholesterol precursor under UV light

Front 17

What are the thyroid hormones produced from the AA tyrosine and are they lipophilic or hydrophilic?

Back 17

T4 (thyroxine) and T3 (triiodothyronine). Lipophilic

Front 18

What is the fate of hydrophobic hormones?

Back 18

Diffuse out of endocrine cell into blood--> immed bind to transport proteins in blood--> diffuse out of blood and into target cell--> bind to nuclear receptors--> induce transcription

Front 19

What are eicosanoids?

Back 19

FA derivatives from an arachidonic acid precursor. (lipophilic hormones)
They usually act locally on a very short half-life (sec-min)

Front 20

What are the two enzymes that convert arachidonic acid to eicosanoids (and what molecules do they make?)?

Back 20

Cyclooxygenase-->prostaglandins
Lipoxygenase-->Leukotrienes

Front 21

What are prostaglandins' main functions?

Back 21

Affecting platelet aggregation, promoting SM contraction (raising BP, increasing uterine contractions).

Front 22

What are leukotrienes' main functions?

Back 22

Mediate inflammation, bronchioconstriction.

Front 23

What do NSAIDs like ibuprofen, naproxen, and aspirin usually target?

Back 23

Cyclooxygenase (COX), the enzyme that converts arachidonic acid to prostaglandins (eicosanoids).

Front 24

When are lipophilic hormones released into blood?

Back 24

Immediately after synthesis.

Front 25

When are lipophilic hormones released from carrier proteins in the blood?

Back 25

When the unbound (or free) concentration of hormone drops, as an equilibrium between bound and unbound hormones is maintained.
Hence measuring free hormone in blood does not accurately reflect available hormone.

Front 26

Breakdown the biosynthesis of peptides and proteins.

Back 26

Translation of ER-bound ribosomes--> polypeptide chains inserted into lumen of ER--> proteins folded in ER--> correctly folded proteins transported to cis-Golgi--> cistrenal progression from cis to trans-Golgi--> mature proteins packaged in secretory vesicles

Front 27

How and where is proinsulin activated?

Back 27

Proinsulin is post-translationally proteolytically cleaved into an active hormone by beta cell peptidases in secretory vesicles in the beta cells of the pancreas

Front 28

How is POMC (proopiomelanocortin) activated?

Back 28

It is post-translationally proteolytically cleaved to form multiple active hormones, with the only human physiological hormone being ACTH.

Front 29

What are the catecholamine hormones derived from the AA tyrosine and are they lipophilic or hydrophilic?

Back 29

Epi and NE. Hydrophilic.

Front 30

How are hydrophilic hormones stored?
How are they secreted?

Back 30

In secretory vesicles (because they cannot cross the lipid bi-layer).
Ex: in adrenal chromaffin cells, and pituitary lactrotroph
They are secreted from the endocrine cell into ECspace through exocytosis.

Front 31

How is exocytosis a therapeutic agent?

Back 31

BoTox (cleaves SNARES, thus preventing synaptic transmission).
Sulfonylureas: antihyperglycemic by inducing ATP-indep't K+ channel closure in the beta cell, thus potentiating insulin secretion

Front 32

What is the fate of hydrophilic hormones in the blood?

Back 32

Endocrine cell secretes active hormones (bc prohormones were cleaved and activated in endocrine cell) which diffuse to the blood--> hormones circulate unbound--> diffuse out of blood and activate surface rec on target cell--> act via second messengers

Front 33

How are hydrophilic hormones broken down?

Back 33

Some are broken down in their end organ, but most circulating hormones are broken down to inactive metabolites in the liver

Front 34

What are a couple common causes of hypofunction in endocrine pathology?

Back 34

Autoimmune destruction, genetic defects in hormone synth pathways/ hormone rec/ intracellular signaling pathways.

Front 35

What is the usual cause of endocrine hyperfunction?

Back 35

Tumors. Ectopic hormone production by tumors is quite common (eg adrenal carcinomas secreting a lot of androgens--> hirsutism in female pts)