Biochemistry of Steroid Hormones

Question 1

2 Types of Steroid Hormones

Answer 1

Corticoids (made in the adrenal cortex) and sex steroids (made in gonads/placenta)

Question 2

Classifications of Steroid Hormones

Answer 2

Based on receptors they bind to. Glucocorticoids, mineralocorticoids, androgens, estrogens and progesterone

Question 3

Glucocorticoids (cortisol) Function

Answer 3

Regulates metabolism, mood, blod pressure, immunity and pain perception

Question 4

Mineralocorticoids (aldosterone) Function

Answer 4

Electrolyte, maintains blood volume

Question 5

Androgens (testosterone) Function

Answer 5

Male reproductive developmment

Question 6

Estrogens Function

Answer 6

Female secondary sexual characteristics and menstural cycle regulation

Question 7

Progesterones Function

Answer 7

Ovulation regulation, pregnancy maintenance

Question 8

Adrenal Cortex Synthesises

Answer 8

Mineralocorticoids, Gluococorticoids and androgens

Question 9

Ovaries Synthesis

Answer 9

Secretes estrogen and progesterone (varying with ovarian cycle)

Question 10

Testes Synthesis

Answer 10

Produces androgens

Question 11

What are similar and different between production organs

Answer 11

All have similar pathways but different Enzymes (tissue specififc)

Question 12

What is a consequence of steroids being lipophilic

Answer 12

Can’t be stored within cells

Question 13

Adrenal Glands Regulatory Factors

Answer 13

Hypothalamic Hypophysiotropic Hormones and Feedback by Target Gland Hormones

Question 14

Hypothalamic Hypophysiotropic Hormones

Answer 14

Corticopin Release Hormone (CRH) from hypothalamus stimulates adrenocorothopic Hormone (ACTH) from anterior pituitary, regulating (positive feedback) adrenal hormone production of cortisol.

Question 15

Target Gland Hormones Outline

Answer 15

Negative feedback through cortisol inhibits hypothalamus and pituitary

Question 16

Steroids Unique Structure

Answer 16

4 linked hydrocarbon rings, hydrocarbon tail and hydroxyl group. Amphipathic (both hydrophobic and hydrophillic)

Question 17

Steroid Characteristics

Answer 17

Permeates membrane (hydrophobic portion), travels independently in blood (hydrophilic portion), binds intracellularly (hydrophobic, influence gene expression), they are stored in cell vesticles (are very stable)

Question 18

Key Steps: Steroid Hormone Synthesis

Answer 18

Hydrocarbon tail shortening, Hydroxylation (adding -OH) of Steroid Nucleus

Question 19

Hydrocarbon Tail Shortening Outline

Answer 19

Part of tail removed via side chain cleavage

Question 20

Steroid Nucleus Hydroxylation

Answer 20

Adding OH groups modifies 4 ring structure to produce functional hormones eg Cholesterol

Question 21

Key Enzymes in Steroid Hormone Synthesis

Answer 21

Cytochrome P450 and StAR

Question 22

Cytochrome P450(/demolase/CYP11A1) Function, substrates and location

Answer 22

Oxidases molecule. Requires oxygen and NADH. Located in endoplasmic reticulum and adrenal gland, ovary and testes mitochondria

Question 23

Steroidogenic Acute Regulatory Protein (StAR)

Answer 23

Uptakes cholesterol into mitochondria

Question 24

What happens to cholesterol in mitochondria

Answer 24

Converted to pregenolone (precursor to all steroid hormones) by cholesterol side chain cleavage. Catalyzed by cytochrome P450

Question 24

Mineralocorticoids Pathway of Progression

Answer 24

Cholesterol to Pregenoione, Progesterone, deoxycortocosterone, corticosterone and aldosterone

Question 25

Progesterone Formation

Answer 25

Pregenolone has enzymes converts 3 -OH group to 3 keto (double-bond O) group. Isomerisation changes delta 5 double bond to delta 4

Question 26

Cortisol Formation

Answer 26

Pogesterone to 17-Hydroxyprogesterone to 11-deoxycortisol to cortisol

Question 27

Cortisol Function

Answer 27

Metabolism: glucogenesis (increase blood glucose), suppresses inflammation and helps body regulate stress

Question 28

11-deoxycorticosterone Formation

Answer 28

Hydroxylation (add -OH) at C-21 on progestetrone by 21-alpha-hydroxase

Question 29

Corticosterone Formation

Answer 29

Hydroxylation of 11-deoxycorticosterone ar C11 by 11-beta-hydroxalase

Question 30

Aldosterone Formation

Answer 30

Hydroxylation (-OH adding) of C18 on corticosterone and Oxidation (O adding or H removing) of C18 to an aldehyde

Question 31

Steroid Hormones Cellular Mode of Action Outline

Answer 31

Diffuse across cell membrane (lipophilic), bind to intracellular receptors, Hormone- receptor complex moves to nucleus and binds to HREs on DNA. This binding regulates gene transcription leading to changes in protein synthesis

Question 32

Alteration of Gene Expression

Answer 32

Alteration to protein synthesis and changes in cellular response.

Question 33

Aldosterone Function

Answer 33

Increases sodium reabsorption in kidneys, balances salt and water. Increases blood volume and pressure

Question 34

Testosterone Function

Answer 34

Promotes muscle growths and male characteristics

Question 35

Estradiol Function

Answer 35

Regulates menstrual cycle and reproductive tissues

Question 36

Addison’s Disease Outline

Answer 36

Result of glucocorticoid deficiency resulting in insufficient cortisol production. Symptoms: fatigue, low blood pressure, weight loss and skin hyperpigmentation

Question 37

Hypoaldosteronism Outline

Answer 37

Mineralocorticoid Deficiency results in insufficent alsosterone. Symptoms: Dehydration, hyponatremia (low blood sodium), hyperkalemia (high potassium) and hypotension

Question 38

Congenital Adrenal Hyperplasia Disorders Outline

Answer 38

Adrenal gland producing insufficient cortisol biosynthesis due to inherited autosomal recessive disorders. Failure to produce cortisol (due to enlarged glands) means loss of negative feed back (no regulation) to HPA axis. Reduced cortisol and aldosterone and androgen overproduction Symptoms vary depending on enzyme(s) effected