L69: Endocrinology Basics (Part II)

Question 1

Where is serotonin converted into melatonin?

Answer 1

pineal gland

Question 2

What is the basic building block of catecholamines

Answer 2

tyrosine

Question 3

What is the basic building block of indolamines

Answer 3

tryptophan

Question 4

What is the rate limiting step of catecholamine synthesis?

Answer 4

Tyrosine to X-dopa via TYROSINE HYDROXYLASE

Question 5

What is the rate limiting step of indolamine synthesis?

Answer 5

Tryptophan to 5-HTP via TRYPTOPHAN HYDROXYLASE

Question 6

What enzyme catalyzes norepinephrine synthesis, and where is it located?

Answer 6

Dopamine B-hydroxylase. Located in adrenal medulla.

Question 7

What cells in the adrenal medulla are homologous to post-synaptic neurons?

Answer 7

Chromaffin cells

Question 8

Entecapone & benzeride carbidopa

Answer 8

inhibit extracellular conversion of L-dopa to 3-OMD and dopamine, respectively

Question 9

MAOA and MAOB inhibitors

Answer 9

prevent monoamine inactivation

Question 10

SSRI

Answer 10

decrease uptake of 5-HT at synaptic cleft. May lead to desensitization of post-synaptic receptors and negative feedback.

Question 11

N-acetyltransferase is the rate-limiting step for making which hormone?

Answer 11

Melatonin

Question 12

4 examples of + feedback

Answer 12

1. partuition - childbirth 2. Lactation 3. Ovulation 4. Blood clotting (5. when your boss says good job)

Question 13

4 examples of positive feedback

Answer 13

1. partuition - childbirth 2. Lactation 3. Ovulation 4. Blood clotting (5. when your boss says good job)

Question 14

Hypothalamus. What level of axis is this?

Answer 14

Tertiary

Question 15

Pituitary. What level of axis is this?

Answer 15

Secondary

Question 16

Breasts, testes, thyroid. What level of axis is this?

Answer 16

Primary

Question 17

Which has a longer half life: ANP or BNP?

Answer 17

BNP - thus its a useful diagnostic tool.

Question 18

BMP. Higher in men or women?

Answer 18

Women

Question 19

BMP. Increases or decreases with age?

Answer 19

increases

Question 20

BMP. Higher with CHF and renal failure, or lower?

Answer 20

HIgher

Question 21

Normal BMP. Rules out what?

Answer 21

CHF

Question 22

Pt. has high baseline TSH. In response to TRH, TSH increases then returns to high baseline. Significance?

Answer 22

Primary failure at level of thyroid. Since thyroid isn’t making T3/T4, then there is no negative feedback to stop pumping out TSH.

Question 23

Pt. has low baseline TSH that doesn’t respond to TRH. Significance?

Answer 23

This means the patient cannot synthesize TSH normally; thus it makes sense he cannot increase TSH in response to TRH. This is indicative of a secondary failure at level of pituitary.

Question 24

Pt. has a slightly higher baseline of TSH, with a protracted return to baseline upon TRH stimulation. Significance?

Answer 24

Tertiary problem at hypothalamus. Slower response to TSH (because pituitary not prepared to recieve TRH for once) and protracted return to baseline.

Question 25

Does age affect circulating hormone levels?

Answer 25

Yes

Question 26

Factors that affect circulating hormone levels. Name 5

Answer 26

1. Age 2. Sex 3. Body weight 4. Time of day 5. Diet

Question 27

NE acts at alpha or beta adrenergic receptors?

Answer 27

Both

Question 28

Where does the conversion from NE to Epi occur?

Answer 28

adrenal medulla

Question 29

95% of 5HT is made where

Answer 29

gut

Question 30

inactivates and degrades catecholamines

Answer 30

COMT

Question 31

What enzyme takes L-DOPA to dopamine?

Answer 31

Dopa decarboxylase (DDC)

Question 32

catalyzes deamination of monoamines (eg. dopamine)

Answer 32

MAO

Question 33

Which of the following enzymes is most active in the dark? A. Tyrosine hydroxylase B. Dopamine beta Hydroxylase C. Trypophan hydroxylase D. N-acetyltransferase (SNA)

Answer 33

D. N-acetyltransferase (SNA) which is located in pineal gland and synthesizes melatonin from 5HT

Question 34

Define preprohormone

Answer 34

Signal-hormone-copeptide

Question 35

define prohormone

Answer 35

hormone-copeptide (no signal sequence)

Question 36

Which of the following are packaged in the vesicle? A. Signal peptide B. Hormone C. copeptide D. Two of the above

Answer 36

D. Hormone and copeptide are packaged into vesicle Eg. Insulin + C-peptide

Question 37

Cholesterol to pregnenalone?

Answer 37

Desmolase (CYP11A1)

Question 38

Corticosterone to aldosterone?

Answer 38

CYP11B2 - aldosterone synthase

Question 39

11-DOC to corticosterone?

Answer 39

CYP11B2 - 11beta hydroxylase

Question 40

progesterone to 11-DOC

Answer 40

CYP21A2 - 21 alpha hydroxylase

Question 41

Steroid abusing body builders need to take _______ when they come off of testosterone.

Answer 41

hCG. This acts like LH. When you come off of T, negative regulation at hypothalamus is lifted, and pituitary starts secreting LH again, but we might need hCG initially to make the transition smoother.