Endocrinology: Pituitary Hormones

Question 1

Location of pituitary gland

Answer 1

sella turcica of sphenoid

Question 2

The anterior pituitary also called? and the posterior pituitary?

Answer 2

anterior pituitary gland–> adenohypophysis

posterior pituitary galnd –> neurohypophysis

Question 3

Most cell types of pituitary gland are

Answer 3

somatotropes (about 40%)

Question 4

Cell types of anterior pituitary gland and the hormones each secretes

Answer 4

*MNEMONIC: Some Think Cody Looks Good.

Somatotropes --> human growth hormone (hGH) 
Thyrotropes --> TSH 
Corticotropes -->ACTH 
Lactotrophes --> PRL (Prolactin) 
Gonadotropes --> LH and FSH

Question 5

Location of cells that synthesize posterior pituitary gland hormones

Answer 5

Hypothalamic supraoptic and paraventricular nuclei

Question 6

Which cells produce posterior pituitary gland hormones?

Answer 6

Magnocelullar neurons

Question 7

Hypothalamic control of pituitary gland secretion

Answer 7

Release hypothalamic releasing or inibitory factors/hormones which inhibit or cause release of pituitary gland hormones

Travel via hypothalamic hypophyseal portal system to reach anterior pituitary gland, while uses purely neuron signals to affect posterior pituitar gland

Question 8

Factors affecting release of hypothalamic inhibitory or releasing factors

Answer 8

Emotional or mental excitation
Levels of nutrients and electrolytes
Olfactory stimulus
Pain

Question 9

Major factors secreted from hypothalamus to anterior pituitary gland

Answer 9

1. Growth hormone releasing hormone
2. Thyrotropin releasing hormone
3. Corticotropin releasing hormone
4. Prolactin inhibitory hormone
5. Gonadotropin releasing hormone

Question 10

Unique feature of GH as compared to other pituitary hormones.

Answer 10

Exerts its effects not by affecting other glands, but directly affecting body cells; it doesn’t have a specific target

Question 11

Which organic molecule’s metabolism is affected in the shortest amount of time by GH?

Answer 11

Protein synthesis

Question 12

Importance of somatomedin C

Answer 12

Is released when liver is stimulated by GH
It carries out effects of GH because it binds more strongly to plasma proteins so has a longer half life and prolonged effects.
People who have congenital deficiency of somatomedin C are generally short because somatomedin C is important in GH effects to be implemented. This is seen in dwarfs

Question 13

Stimulators of GH secretion

Answer 13

Stress (exercise/anxiety) 
Strong emotions 
Starvation 
Hyoglycemia 
Ghrelin

Question 14

Somatomedin also called

Answer 14

Insulin-like growth factor (IGF)

Question 15

GHRH is released from

Answer 15

Hypothalamus ventromedial nucleus

Question 16

Mechanism by which GHRH causes release of GH

Answer 16

by cAMP messenger system

1. GHRH binds to its receptors
2. activation of adenylyl cyclase
3. formation of cAMP
4. increase in calcium concentration = exocytosis of vesicle contents

Also has genomic effect of increasing transcription for synthesis of new growth hormone

Question 17

Regulation of GH secretion

Answer 17

GHRH causes increase in its secretion and Somatostatin causes decrease in its secretion. Feedback mechanism is not clear, but the overall nutritional state determines levels of GH with protein deficiency having greater effect in chronic starvation compared to carbohydrate deficiency in acute starvation

Question 18

Hypopituitarism

Answer 18

Condition in which there is significant reduction in secretion of all anterior pituitary hormones.
No GH = Dwarfism if it occurs in childhood as well as increased risk of osteoperosis and arthritis because osteoblasts are not being as active in bone remodelling

No LH and FSH means loss of sexual function and failure to undergo puberty if this occurs during childhood

No TH means no thyroid hormones produced by thyroid gland = decrease in metabolism, lethargy, and weight gain

Question 19

Why is Gigantism often associated with diabetes?

Answer 19

In gigantism excess GH is produced, but because of its diabetogenic effects (increases insulin resistance), the pancreas beta cells work harder to secrete insulin in response to the hyperglycemia and eventually begin to break down leading to total loss of insulin and full blown diabetes mellitus

Question 20

Normal concentrations of growth hormone

Answer 20

1.6 - 3 ng/ml in adults

6 ng/ml in children and adolescents

Question 21

Cell types of posterior pituitary gland

Answer 21

pituicytes

Question 22

ADH is secreted mainly in the

Answer 22

supraoptic nuclei

Question 23

Why do oxytocin and ADH have slight functional similarities?

Answer 23

Very structurally similar. both have 9 amino acids, but they differ in only two; vasopressin has phenylanine instead of isoleucine and arginine instead of leucine

Question 24

Composition of oxytocin and ADH

Answer 24

ADH/Vasopressin MNEMONIC: Very Cold Tea *Prevents Gas. And Cinnamon Powder *Alleviates Gas.

Vasopressin; Cys, Tyr, Phe, Gly, Asn, Cys, Pro, Arg, Gly
Oxytocin: Cys, Tyr, Ile, Gly, Asn, Cys, Pro, Leu, Gly

Question 25

Mechanism of ADH on renal cells

Answer 25

binds to receptors, causes activation of adenylyl cyclase, increases cAMP levels, causes docking of vesicles with aquaporins. exocytosis causes their release making the cell more permeable to water

Question 26

How is ADH secretion regulated?

Answer 26

When concentration is high in plasma, water moves out of osmoreceptors in or around the hypothalamus causing them to shrink and send signals to hypothalamus to cause increased secretion of ADH.
When concentration is too low, water moves into the osmoreceptors and increases their size causing them to stop sending signals to hypothalamus to cause secretion of ADH

Question 27

Evidence for which oxytocin could be responsible for causing uterine contractions in pregnancy

Answer 27

1. Animals without hypothalamus section responsible for stimulating oxytocin release have prolonged labor
2. Oxytocin levels increase at labor when uterine contractions increase
3. Stimulation of cervix correlated with increase in oxytocin levels