L 10 biosynthesis of steriod hormones

Question 1

juxtacrine signaling

Answer 1

direct physical contact

Question 2

endocrine signaling

Answer 2

-travels fairly far through the blood to a target organ expressing receptor
-low in concentration; high affinity receptor
-minutes to hours

Question 3

paracrine signaling

Answer 3

-travels only a short distance and affects neighboring cells
-fairly high local concentration; receptor with lower affinity
-rapid and localized communication

Question 4

synaptic or neuronal signaling

Answer 4

-neurotransmitter; travels very short distance
-very high local concentration; dissociate rapidly
-very rapid (millisecond) termination

Question 5

autocrine signaling

Answer 5

-made and functions in the same cell
-similar to paracrine signaling

Question 6

steroid hormones

Answer 6

-Synthesized from cholesterol.
-Planar, rigid, and hydrophobic  tight binding to receptors
-Exist in very low concentrations in the body (0.1 – 10 nM).
-Bound to serum carrier proteins.

Question 7

common mode of action of steroid hormones

Answer 7

-free hormones diffuse through the cell membrane and bind to a specific steroid
hormone receptor.
-Regulate transcription of a specific set of genes.

Question 8

sex and progestational hormones steroid hormones

Answer 8

-Progesterone (C-21): female menstrual cycle, pregnancy, embryogenesis
-17β-Estradiol (C-18): estrogen, female hormone
-Testosterone (C-19): androgen, male hormone

Question 9

adrenocortical hormones steroid hormones

Answer 9

-Cortisol (C-21): glucocorticoid, anti-stress hormone, anti-inflammation
-Aldosterone (C-21): mineralocorticoids, regulator of Na+ uptake in the kidney;
raises blood volume and blood pressure

Question 10

bind steroid hormones and regulate transcription of a specific set of genes

Answer 10

-Estrogen receptor
-Androgen receptor
-corticosteroid receptor
-Aldosterone receptor
-Progesterone recepto

Question 11

steroid receptors that belong to nuclear receptor family

Answer 11

-Steroid receptors
-Thyroid hormone receptor
-Retinoic acid receptor
-Vitamin D recepto

Question 12

hormone response element

Answer 12

-DNA-binding domains of activated dimers bind to specific DNA sequences called
Hormone Responsive Elements (HRE), upstream of steroid responsive genes.
-Binding alters the rate of transcription

Question 13

17 alpha hydroxylase deficiency

Answer 13

-Rare form of congenital adrenal hyperplasia (5%)
-Caused by mutations in CYP17A1, which has both 17α-hydroxylase and 17,20-lyase activities.
-Overproduction of mineralocorticoids and deficiency of corticosteroids and sex hormones.

Question 14

symptoms of 17 alpha hydroxylase deficiency

Answer 14

-Hypocortisolism  enlargement of the adrenal glands
- Ambiguous genitalia
-Hyperaldosteronism  hypertension

Question 15

21 hydroxylase deficiency

Answer 15

-Major form of congenital adrenal hyperplasia (95%)
-Mutations in CYP21A2, which functions as 21-hydroxylase

Question 16

symptoms of 21 hydroxylase deficiency

Answer 16

-Hypocortisolism –> enlargement of the adrenal glands
-Hypoaldosteronism–> hyponatremia; can be life-threatening in infants
-Premature androgen exposure
*Ambiguous genitalia in female
*Hirsutism
*Early epiphyseal closure  short stature

Question 17

Transport and excretion of steroids

Answer 17

-Transported in plasma by plasma transport proteins
*Corticoid-binding globulin (transcortin) – glucocorticoids and progesterone
*Sex hormone binding globulin (SHBG) – testosterone and estradiol
-Metabolized in the liver (oxidation, sulfation, and glucuronidation) to soluble forms.
-Excreted in the bile (estrogen) or in the urine (progesterone, androgen, and
glucocorticoids)

Question 18

aminoglutethumide

Answer 18

-therapeutic intervention in steroid synthesis
-inhibits aromatase and P450scc
-Used to block steroid production in some
hormone-dependent tumors (breast,
prostate

Question 19

Ketoconazole (Nizoral ®)

Answer 19

-theraputi intervention in steroid synthesis
-Antifungal at lower concentration (block
the synthesis of ergosterol)
-inhibits P450scc, 17α-hydroxylase, and
11β-hydroxylase
-Can treat hyperglucocorticoid states
(Cushing’s syndrome)
-May cause toxic side effects.

Question 20

non-selective steroidogenesis inhibitors

Answer 20

-Aminoglutethimide (Elipten®, Cytadren®, Orimeten®)
-Ketoconazole (Nizoral ®)