Hypothalamic-Pituitary Relationship and Biofeedback Pt. 1

Question 1

What area do tumors in the pituitary gland expand and impinge on?

Answer 1

Optic nerve

Question 2

What are the 2 hypothalamic nuclei send axons to posterior pituitary?

Answer 2

Supraoptic nucleus

Paraventricular Nucleus

Question 3

What neuropeptides do the hypothalamic nuclei secrete to the posterior pituitary?

Answer 3

ADH (SON)

Oxytocin (PVN)

Question 4

What is the difference in communications between hypothalamus to the anterior pituitary and posterior pituitary?

Answer 4

Posterior pituitary communication = Neural

Anterior pituitary communication = Neural and Hormonal

Question 5

What hormones does the anterior pituitary secrete?

Answer 5

FLAT PeG

FSH, LH, ACTH, TSH, Prolactin, GH

Question 6

How is the anterior pituitary connected to the hypothalamus?

Answer 6

• hypothalamic-hypophysial portal blood vessels

- allows direct delivery to anterior pituitary in high concentrations

Question 7

List the hypothalamic-anterior pituitary hormones, their target, and the hormone secreted

Answer 7

TRH- thyrotrophs- TSH
CRF- corticotrophs- ACTH
GnRH- gonadotrophs- LH, FSH
Somatosatin (-)- somatotrophs- GH
PIF(-)- lactotrophs- PRL
TRH- lactotrophs- PRL

Question 8

Primary endocrine disorder

Answer 8

low/high levels of hormone due to defect in peripheral endocrine gland

Question 9

Secondary endocrine disorder

Answer 9

low/high levels of hormone due to defect in pituitary gland

Question 10

Tertiary endocrine disorder

Answer 10

low/high levels of hormone due to defect in hypothalamus

Question 11

HPG axis in males

Answer 11

1) Hypothalamus releases GnRH into pituitary
2) Pituitary releases LH in Leydig cells and FSH in Sertoli cell
3) Leydig cell produces testosterone and Sertoli cell produces androgen binding protein and sperm

Feedback inhibition from Sertoli cell to pituitary and from testosterone to pituitary and hypothalamus

Question 12

HPG axis in females

Answer 12

1) Hypothalamus releases GnRH into pituitary
2) Pituitary releases LH in Theca cell and FSH in granulosa cell
3) Theca cell secretes androgens and granulosa cell secretes estrogens

Question 13

Function of LH and FSH

Answer 13

• promotes estrogen and progesterone secretion in females

- promotes testosterone production in males

Question 14

How are FSH and LH regulated?

Answer 14

Hypothalamic GnRH pulsatile release; secreted by gonadotrophs

Question 15

Acromegaly

Answer 15

• excessive growth of soft tissue, cartilage, and bone in the face, hands, and feet
• gradual development
• prolonged/excess secretion of GH in adult life

Question 16

What type of cell produces GH?

Answer 16

Somatotropes

Question 17

What organs does GH target?

Answer 17

liver- signal transduction

bone- growth

Question 18

What inhibits GH?

Answer 18

somatostatin, IGF-1

Question 19

What causes stimulation of GH?

Answer 19

• fasting/hunger/starvation
• hypoglycemia
• hormones of puberty
• exercise
• sleep
• stress

Question 20

Direct actions of GH

Answer 20

1) Hypertrophy- increase in size/volume of cells
2) Hyperplasia- increase in number of cells or proliferation rate via mitosis
3) Increase glycogen and fat breakdown for energy; increase protein synthesis

Question 21

Indirect actions of GH

Answer 21

• signals liver to produce insulin like growth factors (IGF)
• targets almost every cell in body
• stimulates hypertrophy and hyperplasia

Question 22

Treatment for defective release of GHRH

Answer 22

Semorelin

tertiary deficiency

Question 23

Treatment for GH replacement

Answer 23

Somatotropin
Somatrem
(secondary deficiency)

Question 24

Treatment for failure of IGF-1 release via GH, GH deficiency, and patients with GH antibodies

Answer 24

Mecasermin

primary deficiency

Question 25

What does excess of growth hormone before closure of bone epiphysis cause?

Answer 25

Gigantism- due to IGF-1 stimulated long bone growth

Question 26

What does excess GH after closure of bone epiphysis closure cause?

Answer 26

Acromegaly- due to promotion of growth of deep organs and cartilaginous tissue

Question 27

What occurs in growth promoting conditions?

Answer 27

1) increased CHO and Pro intake 2) liver produces IGF-1 3) mitogenesis, lypolysis, differentiation

Question 28

What occurs during unfavorable growth conditions?

Answer 28

1) increased CHO intake; decreased Pro intake 2) GH inhibited, liver will not produce IGF-1 3) lipogenesis, CHO storage, weight gain

Question 29

How do growth factors shift in the fasted state?

Answer 29

1) decreased CHO intake; increased Pro intake 2) GH levels increase, liver will produce IGF-1 3) lipolysis, ketogenic metabolism, diabetogenic GH promotes lipolysis, but can also promote insulin insensitivity GH raises blood glucose by decreasing glucose uptake and stimulating hepatic gluconeogenesis

Question 30

Diagnosis for acromegaly

Answer 30

1) elevated serum GH and IGF-1 levels | 2) failure to suppress GH production in response to oral load of glucose

Question 31

When are GH levels highest?

Answer 31

Sleep and exercise

Question 32

During what life stage is GH secretion highest?

Answer 32

Puberty, followed by childhood

Question 33

Results of GH deficiency

Answer 33

- decreased secretion of GHRH, decreased growth hormone secretion - failure to generate somatomedins - GH or somatomedin resistance

Question 34

Results of GH excess

Answer 34

- usually due to GH secreting pituitary adenoma | - consequences depend on developmental stage (before puberty = gigantism; after puberty = acromegaly)

Question 35

What is prolactin synthesized by?

Answer 35

lactotropes

Question 36

When does prolactin secretion begin?

Answer 36

5th week of pregnancy | pulsatile

Question 37

Actions of prolactin

Answer 37

- stimulate and maintain lactation | - suppress GnRH (inhibit LH and FSH) in order to decrease reproductive function and suppress sexual drive

Question 38

How does PRL feedback work?

Answer 38

Prolactin released from the anterior pituitary to the breast inhibits more release by the anterior pituitary via acting on dopamine; also inhibits GnRH release

Question 39

What are the major stimulating factors affecting PRL secretion?

Answer 39

- pregnancy - breast feeding - sleep - stress - TRH

Question 40

What are the major inhibitory factors affecting PRL release?

Answer 40

- dopamine - dopamine agonists - somatostatin - prolactin via negative feedback

Question 41

Causes of hypopituitarism

Answer 41

1) brain damage 2) pituitary tumors 3) non-pituitary tumors 4) infections 5) infarction 6) autoimmune disorders 7) pituitary hypoplasia or aplasia 8) genetic disorders

Question 42

What are the actions of oxytocin released from the posterior pituitary?

Answer 42

1) milk ejection | 2) uterine contraction