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OSSF II Endocrinology > Overview > Flashcards

Overview Flashcards

1
Q

Protein hormones are made where?

A

Hypothalamus
Pituitary gland
Thyroid/parathyroid glands

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2
Q

In the synthesis of protein hormones, hormones enter the golgi complex as ______ and leave as _____.

A

pro hormones

active hormones

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3
Q

The release of protein hormones from secretory vesicles depends on what?

A

Calcium

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4
Q

Steroid hormones are produced by:

A

Adrenal Cortex
Genitals
Kidney, liver, skin (Vitamin D)

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5
Q

What are the three fates of cholesterol?

A
  1. Vitamin D (skin)
  2. Bile Acids (Liver, most)
  3. Pregnenolone
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6
Q

What is the sequence of conversions that cholesterol undergoes in steroid secreting cells?

A
  1. Desmolase converts cholesterol to pregnenolone
  2. Pregnenolone becomes progesterone
  3. Progesterone becomes:
    a. Glucocorticoids (i.e. cortisol)
    b. Mineralocorticoids (aldosterone)
    c. Androgens (testosterone)

Androgens -> estrogens

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7
Q

How are steroids stored?

A

Cholesterol is stored as cholesterol esters in vacuoles; rapidly accessible upon stimulation

Steroid hormones are NOT stored in large amounts

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8
Q

Which 2 factors control secretion of steroids and thyroid hormones (amines), and how long does it take?

A
  1. Amount of substrate (cholesterol ester for steroids, iodine for thyroid hormones)
  2. Availability of enzymes/transporters (StAR for steroids)

Slow (hours to days)

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9
Q

Amines are produced by:

A
  1. Adrenal medulla (catecholamines)

2. Thyroid (thyroid hormones)

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10
Q

Catecholamines are derivatives of which amino acid?

A

Tyrosine

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11
Q

Within the adrenal medulla, where specifically are catecholamines made?

A

Cytosol of chromaffin cells

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12
Q

What are the two catecholamines and which is more abundant?

A
  1. Epinephrine (main)

2. Norepinephrine

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13
Q

Where are catecholamines stored and what stimulates their release?

A

Stored in secretory vesicles

Release stimulated by calcium (sympathetic system)

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14
Q

Within the thyroid, where specifically are thyroid hormones produced?

A

Follicular cells

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15
Q

What are the steps in thyroid hormone synthesis?

A
  1. TG-T3-T4 in colloid enters follicular cell via endocytosis
  2. Endocytic vesicle fuzes w/ lysosomes
  3. Molecules diffuse into cytosol and through cell’s plasma membrane into blood vessel
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16
Q

What are the steps in regulating the endocytosis of TG-T3-T4 into the follicular cells?

A
  1. TSH (from blood vessel) binds TSH receptor (on follicular cell)
  2. ATP -> cAMP
  3. cAMP activates Protein Kinase
  4. Protein kinase activates protein P, triggering endocytosis
17
Q

Where are thyroid hormones stored?

A

Colloid/follicular lumen
*Note that the follicular cells surround this lumen, but the thyroid hormones are not stored within the follicular cells themselves

18
Q

Which hormones are hydrophilic and mostly unbound to plasma proteins?

A

Peptides

Catecholamines (may be loosely bound to albumin)

19
Q

Which hormones are hydrophobic and travel bound to albumin?

A

Iodothyronines (also bind thyroid hormone-binding globulin/TBG)
Steroids

20
Q

Hormone receptors have high _____ but low _____ for hormones.

A 
High affinity (small Kd)
Low specificity
21
Q

Which type of hormone activates transmembrane receptors and which types of reactions do transmembrane receptors induce?

A
  1. Hydrophilic (peptides/catecholamines) activate transmembrane receptors
  2. Transmembrane receptors induce GPCR and protein tyrosine kinases
22
Q

Which type of receptors do hydrophobic hormones activate?

A

Intracellular receptors

23
Q

Where are steroid receptors? Thyroid hormone receptors?

A

Steroids - cytoplasm

Thyroid hormone - nucleus

24
Q

How are protein hormones removed?

A
  • Degraded by proteases in circulation
  • Degraded in lysosomes on cellular receptors
  • SMALL proteins filtered by kidney
25
Q

How are catecholamines removed?

A
  • Reuptake by sympathetic nerves
  • Degraded by MAO (monoamine oxidase) and COMT (catecholamine-O-methyltransferase) in blood, liver, and kidneys
  • Excreted by kidneys (inactive form)
26
Q

Clearance equals

A

Excretion rate / Plasma concentration

(Flow rate) x (hormone concentration in urine) / Plasma concentration

27
Q

Describe negative feedback of the glucocorticoids in the H-P-A axis

A
  1. Hypothalamus activates (anterior) pituitary w/ CRH
  2. (Anterior) pituitary activates adrenal cortex w/ ACTH
  3. Adrenal cortes inhibits hypothalamus and anterior pituitary w/ Cortisol
28
Q

Hormone deficiencies cause:

A

Type 1 diabetes mellitus (destruction of glandular tissue)

Hypothyroidism (low iodine availability)

29
Q

Hormone resistance causes:

A

Type 2 diabetes mellitus

30
Q

The adrenal medulla secretes _____ while the adrenal cortex makes _______.

A

Medulla - catecholamines (epinephrine > norepinephrine)

Cortex - steroids

OSSF II Endocrinology (11 decks)

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