Endocrine III: Hypothalamic-Pituitary Relationship

Question 1

Which hormones are released by the anterior pituitary?

Answer 1

FSH, LH, ACTH, TSH, prolactin, endorphins, GH (FLAT PEG)

Question 2

Which hormones are released by the posterior pituitary?

Answer 2

oxytocin, vasopressin (aka, AVP or ADH)

Question 3

What is known as the “master gland” of the body?

Answer 3

the hypothalamus

Question 4

What is the median eminence (ME)?

Answer 4

It is the floor of the hypothalamus and convergence point for axons.

Question 5

Which hypothalamic nucleus regulates thirst?

Answer 5

PVN and SON

Question 6

Which hypothalamic nucleus regulates mood/emotions/stress?

Answer 6

PVN and ARC

Question 7

Which hypothalamic nucleus regulates BP?

Answer 7

PVN

Question 8

Which hypothalamic nucleus regulates sleep?

Answer 8

SCN

Question 9

Which hypothalamic nucleus regulates circadian rhythms?

Answer 9

SCN

Question 10

Which hypothalamic nucleus regulates feeding behaviors/satiety?

Answer 10

ARC

Question 11

Which hypothalamic nucleus regulates reproduction?

Answer 11

POA

Question 12

Which hypothalamic nucleus regulates body temperature?

Answer 12

POA

Question 13

The hypothalamic-releasing factors all target which gland?

Answer 13

the ANTERIOR pituitary

Question 14

What are two of the characteristic features of Kallman Syndrome?

Answer 14

reproductive failure and anosmia

Question 15

How is GnRH released?

Answer 15

in a pulsatile manner (obligatory!)

Question 16

Gonadotropic hormones have the same ____ subunit but different ____ subunits.

Answer 16

alpha; beta

Question 17

GnRH pulse frequency determines what?

Answer 17

which gonadotropin subunit is released

Question 18

What are the 5 major cell types of the anterior pituitary?

Answer 18

acidophils:

• somatotrophs
• lactotrophs

basophils:
- corticotrophs
- gonadotrophs
- thyrotrophs

Question 19

Why is it important to know whether pituitary hormones have a circadian rhythm?

Answer 19

It is an important consideration when taking blood samples to evaluate endocrine disease.

Question 20

What are Herring bodies?

Answer 20

dilations of unmyelinated axons near their terminals that contain vesicles of AVP or oxytocin plus a binding protein, neurophysin; characteristic of posterior pituitary histology

Question 21

Can releasing hormones be measured in circulation?

Answer 21

No, as they are in the hypophysial portal system and can only be measured in the portal vein. This vein is very tiny, plus releasing hormones have short half-lives, so they cannot be measured in humans.

Question 22

What are the anatomical components of the anterior and posterior pituitary?

Answer 22

• anterior: pars distalis, pars tuberalis, pars intermedia

- posterior: pars nervosa, infundibulum

Question 23

Where is the median eminence located?

Answer 23

lies outside of the BBB and forms the floor of the 3rd ventricle

Question 24

How does GnRH pulse frequency affect expression of LH and FSH transcription?

Answer 24

• high frequency: LH favored

- low frequency: FSH favored

Question 25

Mutations in the KISS1 receptor result in sterility due to a condition called ________.

Answer 25

hypogonadotropic hypogonadism

Question 26

What is the primary function of GnRH?

Answer 26

To stimulate the anterior pituitary to secrete gonadotropic hormones (LH and FSH) for reproductive functions. It is the most upstream hormone regulator of reproduction.

Question 27

What is the etiology of Kallmann syndrome?

Answer 27

Sensory neurons from the olfactory epithelium normally extend axons into the olfactory bulb of the brain. In Kallmann syndrome, the olfactory bulb has degenerated. This means that GnRH-secreting neurons from the olfactory placode also do not migrate through the cribriform plate and into the hypothalamic portion of the brain. Since GnRH neurons fail to enter the CNS, Kallmann syndrome is characterized by reproductive failure.

Question 28

What is the blood supply of the anterior vs. posterior pituitary?

Answer 28

• Anterior: superior hypophysial artery, which gives rise to the portal plexus
• Posterior: inferior hypophysial artery

Question 29

What are the 2 major pathways of the hypothalamus-pituitary connection?

Answer 29

1. Tuberoinfundibular system: neurons that send axonal projections to ME; hormones target AP
2. Neurohypophysial tract: neurons whose axons pass through ME and terminate in PP

Question 30

What are the anterior and posterior pituitary derived from?

Answer 30

• AP is glandular tissue derived from embryonic foregut

- PP is neural tissue derived from neuroectoderm