Pituitary gland and hypothalamus Flashcards Preview

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Flashcards in Pituitary gland and hypothalamus Deck (46):
1

What is the pituitary gland known as?

The master of all endocrine galnds

2

What are structural properties of the pituitary gland?

Size of a pea - 0.5g

Sits at the bottom of the brain -> sella turcica

Broad division into the anterior and posterior pituitary

Pituitary and hypothalamus are one unit -> division relates to how it interacts with the hypothalamus

3

Why are pituitary adenomas often linked to loss of visual acuity?

The pituitary sits adjacet to the branches of the optic nerve

Some of the branches cross over at the levels of the pituitary

Compression of aspects of the optic chiasm if the pituitary expands

4

What characterises the posterior from the anterior pituitary?

The way they interact with the hypothalamus is different

5

What is another name for the anterior pituitary?

Adenophysis

6

How does the hypothalamus communicate to the anterior pituitary?

Anterior pituitary is under the control of hormones (peptides) released by the hypothalamus

Neurosecretory neurons from the hypothalamus secrete the hormones into the venous system that connect the two structures

7

What is the venous system that joins the adenophysis to the hypothalamus called?

Hypophyseal portal system

8

How does the hypothalamus communicate to the posterioi pituitary?

Nervous system

The posterior pituitary is innervated by neurones from the hypothalamus

9

What are the two hormones released from the posterior pituitary?

ADH

Oxytocin

10

When are hormones released from the posterior pituitary?

In situations of stress

11

What are 5 hormones released by the anterior pituitary?

Growth hormone
Thyroid stimulating hormone
Prolactin
ACTH
LH and FSH

12

What are hormones released by the hypothalamus that acts on the anterior pituitary?

Growth hormone releasing hormone
Thyroid releasing hormone
CRH
GnRH

13

What happens in the hypothalamic pituitary thyroid axis?

1. TRH is released from the hypothalamus

2. Stimulates the anterior pituitary to release TSH

3. Acts on the thyroid to release T3 and T4

14

How is TRH release regulated?

In a dional fashion. High and low concentrations throughout the say. Many nervous stimuli affects its release.

15

Features of TRH

Thyrotropin releasing hormone

Highly stable

Tripeptide amine

Rapidly degraded by plasma

16

Where can dysregulation in the thyroid axis happen?

In 3 areas:

Thyroid gland - primary thyroid problem

Pituitary gland - secondary thyroid problem

Hypothalamus - tertiary thyroid problem

17

Where is GnRH released from?

The hypothalamus

18

What is released when GnRH stimulates the anterior pituitary?

LH - Leutinizing hormone

FSH - Follicle stimulating hormone

19

What is LH and FSH involved in?

Development of secondary sexual characteristics

20

In what pattern is GnRH released?

Pulsatile release

21

What would happen if GnRH would be released constantly?

Cause the suppression of FSH and LH

Downregulation of receptors to GnRH on the pituitary

Can be used therapeutically to treat:

1. Early puberty - constant GnRH to suppress LH and FSH receptors

2. Cancer responsive to hormones - testosterone in prostate and oestrogen in breast cancer

22

What conditions can affect the concentration of hormones released by the pituitary?

Gender

State of developmental activity

How much the pituitary has been stimulated

23

What happens if GnRH is released under the right conditions and stimuli?

Spermatogenesis in males

Ovulation in females

24

What hormone is released from the hypothalamus to stimulate GH secretion?

Growth hormone releasing hormone

GHRH

25

What two ways are there of measuring growth?

Hypertrophy - cells get bigger

Hyperplasia - more cells

26

What conditions are related to GH dysregulation?

Acromegaly

Pituitary adenoma

Some types of Dwarfism

27

How do pituitary adenomas dysregulate GH secretion?

Increased GH secretion by the anterior pituitary

Can also release other hormones like prolactin and ACTH

Adenomas are classified by their size

Less than 10 mm -> microadenoma
More than 10mm -> macroadenoma

28

Pathogenesis of acromegaly

Excess release of GH from the pituitary

Symptoms:

Excess growth of soft tissues
Metabolic abnormalities - diabetes
Linear growth
Galactorrhea - abnormal prolactin signalling

29

How does a dysregulation of GH from pituitary lead to dwarfism?

GH resistance or receptor to GH is mutated

30

What hormone acts as a negative regulator of GH release?

Somatostatin

31

What do cortisol and GH have in common?

They are both stress hormones

Excess GH -> insulin resistance, increased lipolysis and acts downstream through IGF 1 made by hepatocytes

32

What do prolactin and GH have in common?

Both structurally similar

33

What roles does prolactin play in the body?

Initiates and maintains lactation

Inhibits GnRH

34

What makes prolactin different from the other hormones produced by the anterior pituitary?

It is not controlled by a releasing factor

Dopamine produced by the hypothalamus regulates the release of prolactin

Decrease in dopamine production => increase in prolactin secretion

35

What is prolactinoma?

Increase in prolactin produced

Most common secretory type of pituitary adenoma

36

What is the difference in presentation of prolactinoma in men and women?

Men present earlier - inhibition of testosterone manifests earlier

37

What suppresses prolactin release?

Dopamine

38

What are treatment options for prolactinoma sufferers?

Surgery - hypophysectomy

Dopamine agonists to suppress prolactin secretion

39

What is another way by which prolcatin can be secreted in excess?

If there is damage to the pituitary stalk

Hypophyseal vein carries dopamine from the hypothalamus to the anterior pituitary

If dopamine doesn't reach pituitary = increased prolactin secretion

40

What hormone is released by the hypothalamus to stimulate ACTH release from the anterior pituitary?

CRH

41

What hormone is released from the anterior pituitary on activation by CRH?

ACTH

42

What organ does ACTH affect?

Adrenal gland

43

What does CRH stand for?

Corticotropin releasing hormone

44

What hormones are released from the adrenal gland upon acrivation with ACTH?

Cortisol - released on psychological and physical stress

Adrenal androgens

45

Why do conditions where there is dysregulation of ACTH often present with pigmentation problems?

ACTH and MSH (melanocortin stimulating hormone) are both peptides.

They both derive from the same precursor POMC

Increased ACTH = increased POMC

Increased POMC = increased MSH = increased pigmentation

46

Addison's disease

Characterised by a decreased production of glucocorticoids and mineralocorticoids

Loss of negative feedback loop means that excess ACTH is produced in response

Damage to the adrenal gland/ mutation to the ACTH receptor or resistance to ACTH