Hypothalamic Pituitary Axis - 2/2 Lopez

Question 1

What is the connection between the hypothalamus and posterior lobe like?

Answer 1

Neural

Question 2

The connection between the hypothalamus and anterior lobe are what?

Answer 2

Neural and endocrine

Question 3

How do hormones get from the hypothalamus to the anterior lobe of the pituitary?

Answer 3

Hypothalamic-hypophysial portal vessels

Question 4

What is a primary endocrine disorder due to a defect in?

Answer 4

Peripheral endocrine gland (target tissue i.e. Thyroid gland)

Question 5

What is a secondary endocrine disorder due to?

Answer 5

Defect in pituitary gland

Question 6

What is a tertiary endocrine disorder due to?

Answer 6

Defect in hypothalamus

Question 7

What are some examples of primary endocrine disorders?

Answer 7

Thyroid, adrenal cortex, liver, gonads

Question 8

What are the most prominent cell types within the pituitary gland?

Answer 8

Somatotrophs (50%)

Question 9

What do corticotrophs release?

Somatotrophs?

Answer 9

ACTH

growth hormone

Question 10

What hormone has melanocyte-stimulating hormone activity?

INC in blood levels of what can cause skin pigmentation?

Answer 10

ACTH

MSH

Question 11

What disease is associated with INC levels of ACTH?

Symptoms?

Answer 11

Addison’s disease

Skin pigmentation

Question 12

What is a main regulator of the HPA axis that stimulates it?

Answer 12

Stress (physical, emotional, chemical)

Question 13

What does ACTH cause the release of in the adrenal gland that can cause negative feedback of the system?

Answer 13

Cortisol or aldosterone

Question 14

What 2nd messenger does the HPT axis use once TRH is released?

What does this activate?

Answer 14

PLC

INC in Ca and PKC

Question 15

After the pituitary thyrotrope has been activated, what does it release?

Answer 15

TSH

Question 16

Once TSH has been released from the pituitary thyrotrope what does it stimulate?

What are its effects?

Ultimate end secretion product?

Answer 16

PKA

Thyroid hormone synthesis and secretion, cell growth

T3, T4

Question 17

What inhibits TRH secretion?

What end product can also inhibit the HPT axis via negative feedback?

Answer 17

Stress

T3

Question 18

What stimulates the synthesis and secretion of GH And where is this initial stimulus located?

What does this hormone act on to release GH?

Answer 18

GHRH from the hypothalamus

Acts on ant. Pituitary

Question 19

What inhibits the secretion of GH?

How?

Answer 19

Somatostatin

Blocks response of ant. Pituitary to GHRH

Question 20

When GH acts on target tissues (liver) what is produced?

How do they inhibit further secretion of GH?

Answer 20

Somatomedins (IGF)

Inhibit release from ant. Pituitary AND stimulate secretion of somatostatin from hypothalamus

Question 21

How is GH secreted?

Answer 21

Pulsatile pattern, burst of secretion every 2 hours

Question 22

What tissues are the main targets of direct effect of GH?

Indirect?

Answer 22

Skeletal m., liver, adipose

Liver

Question 23

What are the direct effects of GH?

What is the net result?

Answer 23

Diabetogenic: DEC glucose uptake into cells
INC lipolysis in adipose
INC protein synthesis in muscle
INC production of IGF

INC in blood [glucose] and blood insulin levels

Question 24

What are the indirect effects of GH?

Answer 24

INC Protein synthesis and organ growth (INC uptake of a.a.)

INC linear growth (INC metabolism in cartilage-forming cells and chondrocytes)

Question 25

What causes GH deficiency?

Answer 25

Lack of ant. Pituitary GH DEC GHRH due to hypothalamic dysfunction Failure to generate IGF in liver GH receptor deficiency

Question 26

GH excess causes what? Mostly due to what?

Answer 26

Acromegaly GH-secreting pituitary adenocarcinoma

Question 27

What does excess GH cause before puberty? After?

Answer 27

Gigantism (INC linear growth) INC periosteum bone growth, INC organ size, glucose intolerance

Question 28

How to treat GH deficiency? Excess?

Answer 28

HGH Somatostatin analogue (octreotide)

Question 29

What does lactogenesis induce the synthesis of?

Answer 29

Lactose, casein and lipids

Question 30

What inhibits lactation during pregnancy even though prolactin levels are high?

Answer 30

High levels of estrogen and progesterone down-regulate prolactin receptors

Question 31

What does prolactin suppress? How?

Answer 31

Ovulation DEC synthesis and release of GnRH

Question 32

What causes prolactin deficiency? Result?

Answer 32

Destruction of ant. Pituitary or lactotrophs Inability to lactate

Question 33

What causes prolactin excess? Result?

Answer 33

Destruction of hypothalamus or hypophysial tract, prolactinomas, Galactorrhea and infertility

Question 34

How to treat prolactin excess?

Answer 34

DA receptor agonist (bromocriptine)

Question 35

What is Sheehan syndrome?

Answer 35

Pituitary in pregnancy is enlarged and more vulnerable to infarction

Question 36

What is Cushing's disease?

Answer 36

Pituitary tumors stimulating an increase in cortisol

Question 37

Pituitary adenomas develop in 25% of patients with what?

Answer 37

MEN 1

Question 38

What is the precursor peptide for ADH? Oxytocin?

Answer 38

Preprossophysin Prepro-oxyphysin

Question 39

What are the triggers for ADH secretion?

Answer 39

DEC BP DEC arterial stretch due to low blood volume INC Osmolarity (>280) MAIN stimulus

Question 40

What are the actions of ADH? Ultimate result?

Answer 40

INC H20 reabsorption via V2 receptors Vasoconstriction via V1 receptor INC BP and INC blood volume

Question 41

What mechanism do the V1 receptors work through? V2?

Answer 41

IP3/Ca cAMP

Question 42

What channel does ADH activate? Where?

Answer 42

aquaporin 2 (AQP2) Principal cells of the late DCT and CD

Question 43

What is ADH secretion like in hyper osmolarity? Urine concentration?

Answer 43

ADH INC urine more concentrated

Question 44

What happens to ADH in hypoosmolarity? Urine concentration?

Answer 44

Less ADH secreted Urine more dilute

Question 45

What are the characteristics of General DI?

Answer 45

Lack of effect of ADH Frequent urination Large volume of urine is diluted

Question 46

What is the cause of central DI? From what?

Answer 46

Lack of ADH Pituitary damage or destruction of the hypothalamus

Question 47

What is happening nephrogenic DI? Cause?

Answer 47

Kidneys unable to respond to ADH (INC plasma ADH) Lithium, polycystic kidney disease, sickle cell anemia

Question 48

What drug is used to treat central DI? Nephro DI?

Answer 48

Desmopressin NONE

Question 49

What is SIADH? What is it characterized by?

Answer 49

excessive secretion of ADH, excessive water secretion Hypoosmolarity and hyponatremia

Question 50

How to treat SIADH?

Answer 50

Fluid restriction IV hypertonic saline (3%) V2 receptor antagonist Demeclocycline (inhibits cAMP)

Question 51

What are the 3 hypothalamic-pituitary axises? What do they control?

Answer 51

thyroid, adrenal, gonads (HPT, HPA, HPG) Growth, milk production/ejection, osmoregulation