Endocrine Physio of the HPEO

Question 1

4 actions of growth hormone

Answer 1

Stimulates bone growth
Protein synthesis
Lipid/carbohydrate metabolism
Synthesis/secretion of IGF1

Question 2

Relationship between GH and insulin

Answer 2

GH is counter regulatory
Opposes insulin action and raises blood glucose
Directly acts on the liver

Question 3

Role of IGF1

Answer 3

Main hormone for long bone growth

Question 4

4 things that can cause GH release

Answer 4

Stress
Exercise
Hypoglycemia
Sleep rhythms

Question 5

What inhibits GHRH secretion?

Answer 5

Somatostatin

Question 6

Types of feedback in the GH pathway

Answer 6

Long
Short
Ultra-short

Question 7

4 functions of prolactin

Answer 7

Lactation
Testis and prostate
Growth and development (potentially)
Immune function

Question 8

What is the main stimulus for prolactin secretion?

Answer 8

Removal of dopamine (inhibitory)

Question 9

Types of feedback in the prolactin pathway

Answer 9

Ultra-short

Short

Question 10

2 Functions of ACTH

Answer 10

Stimulates production and secretion of glucocorticoids

Stress response/homeostasis

Question 11

Somatostatin is (potentially) involved in what 2 pathways?

Answer 11

GH

ACTH (possibly)

Question 12

Difference between
1. Long
2. Short
3. Ultra-short
feedback loops

Answer 12

1. Target hormone feeds back
2. Anterior pituitary hormone feeds back on the hypothalamus
3. Anterior pituitary hormone feeds back on the pituitary

Question 13

2 functions of TSH

Answer 13

Stimulates production and secretion of thyroid hormones

Thyroid growth

Question 14

What type of feedback is there in the TSH pathway?

Answer 14

Long (the only one!)

Question 15

2 functions of LH

Answer 15

Stimulates biosynthesis of testosterone by leydig cells

Regulates production of progesterone and estrogen

Question 16

2 functions of FSH

Answer 16

Regulates spermatogenesis and stimulates production/secretion of inhibin from Sertoli cells
Regulates production of progesterone, estrogen, inhibin and activin

Question 17

If a patient is hypothyroid because they have a primary thyroid defect, what would you expect TSH levels to be?

Answer 17

High

No feedback from the target hormones

Question 18

What 2 hormones can be tested with insulin administration?

Answer 18

GH

ACTH

Question 19

Testosterone biosynthesis

Answer 19

Derived from cholesterol (steroid hormone)
Leydig cells synthesize and secret testosterone
Can also be produced in the adrenal cortex and derived from other steroid precursors in peripheral tissues

Question 20

Is most testosterone free or bound?

Answer 20

Bound to serum proteins (98%)

Albumin or sex-hormone binding globulin

Question 21

Some physiological effects of testosterone

Answer 21

Development of external and internal genitalia, maturation of sexual organs
Androgens determine male secondary sexual characteristics
Spermatogenesis
Sexual function (sexual desire, sleep-induced erections)
Maintenance of bone density, promotes linear bone growth
Muscle development and growth, nitrogen retention
Maintenance of normal red cell mass, Hb
Cognitive effects

Question 22

What would you expect circulating LH and FSH to be if
1. Primary
2. Secondary
hypogonadism?

Answer 22

1. High

2. Low or inappropriately normal

Question 23

Circadian (diurnal) rhythm

Answer 23

24 hours
Most common type
Often driven by light/dark
Ex: cortisol

Question 24

Ultraradian rhythm

Answer 24

Pulsatile
<24 hours
Very short rhythm
Ex: GnRH, GH, LH, FSH

Question 25

Infraradian rhythm

Answer 25

> 24 hours

Ex: Menstrual cycle

Question 26

Should you measure at morning or midnight for

1. Cushing’s
2. Adrenal insuffiency

Answer 26

1. Midnight (should be low, but with C will be high)

2. Morning (should be high, but with AI will be low)