L69: Endocrinology Basics (Part II) Flashcards
Where is serotonin converted into melatonin?
pineal gland
What is the basic building block of catecholamines
tyrosine
What is the basic building block of indolamines
tryptophan
What is the rate limiting step of catecholamine synthesis?
Tyrosine to X-dopa via TYROSINE HYDROXYLASE
What is the rate limiting step of indolamine synthesis?
Tryptophan to 5-HTP via TRYPTOPHAN HYDROXYLASE
What enzyme catalyzes norepinephrine synthesis, and where is it located?
Dopamine B-hydroxylase. Located in adrenal medulla.
What cells in the adrenal medulla are homologous to post-synaptic neurons?
Chromaffin cells
Entecapone & benzeride carbidopa
inhibit extracellular conversion of L-dopa to 3-OMD and dopamine, respectively
MAOA and MAOB inhibitors
prevent monoamine inactivation
SSRI
decrease uptake of 5-HT at synaptic cleft. May lead to desensitization of post-synaptic receptors and negative feedback.
N-acetyltransferase is the rate-limiting step for making which hormone?
Melatonin
4 examples of + feedback
- partuition - childbirth 2. Lactation 3. Ovulation 4. Blood clotting (5. when your boss says good job)
4 examples of positive feedback
- partuition - childbirth 2. Lactation 3. Ovulation 4. Blood clotting (5. when your boss says good job)
Hypothalamus. What level of axis is this?
Tertiary
Pituitary. What level of axis is this?
Secondary
Breasts, testes, thyroid. What level of axis is this?
Primary
Which has a longer half life: ANP or BNP?
BNP - thus its a useful diagnostic tool.
BMP. Higher in men or women?
Women
BMP. Increases or decreases with age?
increases
BMP. Higher with CHF and renal failure, or lower?
HIgher
Normal BMP. Rules out what?
CHF
Pt. has high baseline TSH. In response to TRH, TSH increases then returns to high baseline. Significance?
Primary failure at level of thyroid. Since thyroid isn’t making T3/T4, then there is no negative feedback to stop pumping out TSH.
Pt. has low baseline TSH that doesn’t respond to TRH. Significance?
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.
Pt. has a slightly higher baseline of TSH, with a protracted return to baseline upon TRH stimulation. Significance?
Tertiary problem at hypothalamus. Slower response to TSH (because pituitary not prepared to recieve TRH for once) and protracted return to baseline.
Does age affect circulating hormone levels?
Yes
Factors that affect circulating hormone levels. Name 5
- Age
- Sex
- Body weight
- Time of day
- Diet
NE acts at alpha or beta adrenergic receptors?
Both
Where does the conversion from NE to Epi occur?
adrenal medulla
95% of 5HT is made where
gut
inactivates and degrades catecholamines
COMT
What enzyme takes L-DOPA to dopamine?
Dopa decarboxylase (DDC)
catalyzes deamination of monoamines (eg. dopamine)
MAO
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)
D. N-acetyltransferase (SNA)
which is located in pineal gland and synthesizes melatonin from 5HT
Define preprohormone
Signal-hormone-copeptide
define prohormone
hormone-copeptide (no signal sequence)
Which of the following are packaged in the vesicle?
A. Signal peptide
B. Hormone
C. copeptide
D. Two of the above
D.
Hormone and copeptide are packaged into vesicle
Eg. Insulin + C-peptide
Cholesterol to pregnenalone?
Desmolase (CYP11A1)
Corticosterone to aldosterone?
CYP11B2 - aldosterone synthase
11-DOC to corticosterone?
CYP11B2 - 11beta hydroxylase
progesterone to 11-DOC
CYP21A2 - 21 alpha hydroxylase
Steroid abusing body builders need to take _______ when they come off of testosterone.
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.
