Hypothalamic-Pituitary Adrenal Axis: Hormones and Assessment of Function

Question 1

What 3 parts make up the hypothalamic-pituitary Adrenal Axis (HPA axis)?

Answer 1

1 - hypothalamus
2 - pituitary gland
3 - adrenal gland

Question 2

The 3 parts make up the hypothalamic-pituitary Adrenal Axis (HPA axis) are the hypothalamus, pituitary and adrenal gland. What connects the hypothalamus and the pituitary gland?

Answer 2

• pituitary stalk

Question 3

The 3 parts make up the hypothalamic-pituitary Adrenal Axis (HPA axis) are the hypothalamus, pituitary and adrenal gland. What hormone does the hypothalamus secrete to stimulate the anterior pituitary gland?

Answer 3

• Corticotrophin Releasing Hormone [CRH]

Question 4

The 3 parts make up the hypothalamic-pituitary Adrenal Axis (HPA axis) are the hypothalamus, pituitary and adrenal gland. What hormone does the anterior pituitary gland secrete to stimulate the adrenal gland?

Answer 4

• Adrenocorticotropic Hormone [ATCH]

Question 5

The 3 parts make up the hypothalamic-pituitary Adrenal Axis (HPA axis) are the hypothalamus, pituitary and adrenal gland. The anterior pituitary gland secretes Adrenocorticotropic Hormone (ATCH) to stimulate the adrenal gland. What is then released from the adrenal gland, specifically the cortex?

Answer 5

• glucocorticoids

- specifically cortisol

Question 6

The 3 parts make up the hypothalamic-pituitary Adrenal Axis (HPA axis) are the hypothalamus, pituitary and adrenal gland. The anterior pituitary gland secretes Adrenocorticotropic Hormone (ATCH) to stimulate the adrenal gland. The adrenal gland, specifically the cortex releases glucocorticoids, specifically cortisol. Although this stimulates tissue as part of the stress response, what else are glucocorticoids involved with?

Answer 6

• negative feedback loop
• inhibits hypothalamus and pituitary gland
• reduction in corticotrophin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH)
• overall regulates cortisol levels

Question 7

What is the inferior aspect of the hypothalamus called and what does it go on to create?

Answer 7

• median eminence

- creates the pituitary stalk, also known as the infundibulum

Question 8

The inferior aspect of the hypothalamus is called the median eminence and creates the pituitary stalk, also referred to as the infundibulum. What does this then go onto form?

Answer 8

• posterior pituitary gland

Question 9

There are a group of nuclei within the base of the hypothalamus that regulate the anterior pituitary gland. What is the name given for this group of nuclei?

Answer 9

• tuberal nuclei

Question 10

The hypothalamus has a myriad of functions. What is the primary function of the mamillary bodies that we can see in the image below?

Answer 10

• regulate feeding reflexes (swallowing)

Question 11

The hypothalamus has a myriad of functions. What is a key function the hypothalamus is involved that is able to modulate blood pressure and heart rate for example?

Answer 11

• autonomic control

Question 12

The hypothalamus has a myriad of functions. What is the primary function of the supraoptic nucleus that we can see in the image below?

Answer 12

• secretes anti-diuretic hormone (ADH)
• anti - against
• diuretic = diuresis (urinating a lot)

Question 13

The hypothalamus has a myriad of functions. The primary function of the supraoptic nucleus that we can see in the image below is to secrete anti-diuretic hormone (ADH). What is the purpose of secreting ADH?

Answer 13

• ADH regulates osmolarity (ion concentration in blood, Na+, K+ etc…) and fluid levels
• signal the retention of fluid by the kidneys and vasoconstrict blood vessels to maintain blood pressure
• helps dilute osmolarity

Question 14

The hypothalamus has a myriad of functions. The primary function of the supraoptic nucleus is to secrete anti-diuretic hormone (ADH), which acts to reduce fluid loss from the body. Is ADH then secreted from the anterior or posterior pituitary gland?

Answer 14

• posterior

Question 15

The hypothalamus has a myriad of functions. The primary function of the supraoptic nucleus is to secrete anti-diuretic hormone (ADH), which acts to reduce fluid loss from the body. ADH travels to the posterior pituitary gland via axons from the supraoptic nucleus. What is present in these axons and what is the purpose of them?

Answer 15

• these axons contain out pouchings called herring bodies

- herring bodies store ADH

Question 16

What is the primary function of the tuberal nuclei?

Answer 16

• control of the pituitary gland

Question 17

The hypothalamus has a myriad of functions. What is the primary function of the paraventricular nucleus?

Answer 17

• synthesis of oxytocin

Question 18

The hypothalamus has a myriad of functions. What is the primary function of the suprachiasmatic nucleus?

Answer 18

• control of circadian rhythm

Question 19

The hypothalamus has a myriad of functions. What is the primary function of the preoptic areas?

Answer 19

• thermoregulation

Question 20

The posterior lobe of the pituitary gland is also referred to as the neurohypophysis, which means what?

Answer 20

• neuro = neurologically developed
• hypo = under
• physis = growth

Question 21

The anterior lobe of the pituitary gland, which developed embryonically from the pharynx is also referred to as the adenohypophysis, which means what?

Answer 21

• adeno = gland
• hypo - under/below
• physis = growth

Question 22

The main purpose of the pituitary gland is to synthesis and secrete hormones. Are both the anterior and posterior lobes of the pituitary gland able to synthesise and secrete hormones?

Answer 22

• anterior = yes

- posterior = secrete only

Question 23

What does the anterior pituitary gland secrete that stimulates the adrenal glands?

Answer 23

• adrenocorticotropic hormone (ACTH)

Question 24

What does the anterior pituitary gland secrete that stimulates the ovaries and testes?

Answer 24

• follicle-stimulating hormone (FSH)

Question 25

What does the anterior pituitary gland secrete that stimulates the ovaries and testes alongside Follicle-stimulating hormone (FSH)?

Answer 25

- Luteinizing hormone (LH)

Question 26

What does the anterior pituitary gland secrete that stimulates muscle, fat, liver and bones and is critical for growth and development?

Answer 26

- growth hormone

Question 27

What does the anterior pituitary gland secrete that stimulates breast milk production?

Answer 27

- prolactin

Question 28

What does the anterior pituitary gland secrete that stimulates the thyroid gland?

Answer 28

- thyroid stimulating hormone

Question 29

The posterior pituitary gland is unable to synthesise hormones and therefore these must be synthesised and stored somewhere before being transported to the posterior pituitary gland. Where is this?

Answer 29

- oxytocin synthesised in paraventricular nucleus - anti-diuretic hormone synthesised in supraoptic nucleus - stored in herring bodies of axons from hypothalamus to posterior pituitary gland within the median eminence

Question 30

What 2 key hormones does the posterior pituitary gland secrete?

Answer 30

- anti-diuretic hormone (ADH) | - oxytocin

Question 31

What main artery does the pituitary gland receives its blood supply from, and what are the main smaller branches supplying the pituitary gland?

Answer 31

- internal carotid artery | - hypophyseal branches

Question 32

The main artery that supplies the pituitary gland is the internal carotid artery. This then has 2 main branches that directly supply the upper and lower aspects of the pituitary gland. What are these called?

Answer 32

1 - superior hypophyseal | 2 - inferior hypophyseal

Question 33

The main artery supplying the pituitary gland is the internal carotid artery. This then has 2 main branches that directly supply the pituitary gland, the superior and inferior hypophyseal. What do the superior hypophyseal and inferior hypophyseal supply directly?

Answer 33

- superior hypophyseal artery = pituitary stalk, which drains into portal vessels - inferior hypophyseal artery = posterior lobe draining into the cavernous sinus

Question 34

Roughly what % of the adrenal glands is composed of the medulla and cortex?

Answer 34

- adrenal medulla = 10% | - adrenal cortex (outer layer) = 90%

Question 35

The adrenal glands are composed of the medulla and cortex. Which is associated with acute and chronic stress?

Answer 35

- adrenal medulla = acute | - adrenal cortex (outer layer) = chronic and Na+ and glucose homeostasis

Question 36

The adrenal cortex can be subdivided into 3 areas, and each of these contains specific enzymes, meaning each zone is able to synthesise different hormones. Using the labels below label the 3 zones of the adrenal cortex? zona glomerulosa zona fasciculata zona reticularis

Answer 36

1 - zona glomerulosa 2 - zona fasciculata 3 - zona reticularis

Question 37

The adrenal cortex can be subdivided into 3 areas, and each of these contains specific enzymes, meaning each zone is able to synthesise different hormones, as seen in the image below. Using the labels below, which zone synthesises which hormones in the 3 zones? ``` Adrenal androgens ( androgen precursors) Glucocorticoids [e.g. cortisol] Mineralocorticoids [e.g. aldosterone] ``` (remember the deeper it gets the sweeter it gets)

Answer 37

1 - Mineralocorticoids [e.g. aldosterone] 2 - Glucocorticoids [e.g. cortisol] 3 - Adrenal androgens ( androgen precursors)

Question 38

Does the release of adrenocorticotropic hormone from the pituitary gland secrete continuously or are there times when it peaks?

Answer 38

- it is pulsatile - peaks early morning - lowest at night (melatonin is highest during darkness) CAN BE ALTERED BY CHRONIC STRESS AND/OR LONG HAUL FLIGHTS

Question 39

The release of adrenocorticotropic hormone (ACTH) from the pituitary gland secrete are slowly continuous, but peaks early morning and dips in the middle of the night. What would cause a spike in ACTH?

Answer 39

- perception of stress

Question 40

What is the Cortisol Awakening Response?

Answer 40

- cortisol peaks when we wake, normally 30-45 minutes after waking - preparation for any potential dangers

Question 41

What % of cortisol within the blood is free and not bound to plasma proteins?

Answer 41

- 10%

Question 42

10% of cortisol within the blood is free and not bound to plasma proteins. What plasma proteins does the other 90% bind with?

Answer 42

- albumin = 15% | - corticosteroid binding globulin (CBG) also known as transcortin = 75%

Question 43

10% of cortisol within the blood is free and not bound to plasma proteins. Albumin = 15% and corticosteroid binding globulin (CBG) also known as transcortin = 75%. What happens during pregnancy to the the CBG levels?

Answer 43

- CBG levels increase - modulates the circulating plasma cortisol concentrations - free cortisol remains stable though

Question 44

What is the main mineralocorticoids secreted by the most outer layer of the cortex called the zona glomerulosa?

Answer 44

- aldosterone

Question 45

What is the main function of aldosterone?

Answer 45

- stimulates mineralocorticoid receptors in the distal tubules and collecting ducts of the nephron - influences reabsorption of Na+ and retention of H2O - increases the excretion of K+ - contributes to maintaining blood volume and blood pressure

Question 46

Aldosterone is the main mineralocorticoids secreted by the most outer layer of the cortex called the zona glomerulosa. What system is the main stimulus for initiating the secretion of this hormone?

Answer 46

- renin-angiotensin-aldosterone (RAAS) system

Question 47

In addition to the renin-angiotensin-aldosterone [RAAS] system, what else can contribute to the secretion of aldosterone?

Answer 47

- trauma - anxiety - hyperkalaemia - hyponatraemia - INHIBITED by atrial natriuretic peptide released by heart, which tries to remove fluid and Na+)

Question 48

How much of aldosterone is bound to plasma proteins?

Answer 48

- aprox 50%

Question 49

What does acromegaly mean?

Answer 49

- acro is greek for extremities of the body - megaly is greek for enlarged - caused by excessive levels of growth hormone

Question 50

What is growth hormone acromegaly?

Answer 50

- excessive levels of growth hormone causing abnormal growth | - mainly affects hands, feet, forehead, jaw and nose

Question 51

Growth hormone acromegaly is excessive levels of growth hormone causing abnormal growth, mainly affecting the hands, feet, forehead, jaw and nose. What is the main cause of this?

Answer 51

- pituitary adenoma (benign growth) | - treated with surgery and/or radiotherapy

Question 52

What is Cushing syndrome?

Answer 52

- endocrine disorder causing elevated cortisol in the blood

Question 53

What is the difference between endogenous and exogenous cushings?

Answer 53

- exogenous = factors outside the body are the cause | - endogenous caused by factors within the body

Question 54

What is the main cause of endogenous Cushings?

Answer 54

- pituitary tumour - causes increased levels of adrenocorticotropic hormone (ACTH) - continuous stimulation of the adrenal cortex zona fasciculata (middle layer of the adrenal cortex) - means continuous release of cortisol

Question 55

What are some of the most common features of cushings?

Answer 55

- weight gain (mid region specifically) - fragile and bruised skin - muscle and bone soreness

Question 56

To diagnose cushings what can we measure?

Answer 56

- cortisol in blood, urine and saliva | - identify tumour using imaging

Question 57

What is prolactinoma?

Answer 57

- prolactin = hormone involved in breast milk production - oma = tumour - excessive secretion of prolactin

Question 58

Prolactinoma is the excessive secretion of prolactin. What can this cause in women?

Answer 58

- changes in menstrual cycle - mood disturbances - galactorrhoea (production of breast milk in those who are not pregnant/recently delivered)

Question 59

What is the main cause of prolactinoma, the excessive secretion of prolactin?

Answer 59

- tumour on pituitary gland | - cause is really unknown

Question 60

What does hypopituitarism mean?

Answer 60

- hypo = lower | - pituitarism = inflammation of the pituitary gland

Question 61

What is hypopituitarism?

Answer 61

- lower or lack of secretion/synthesis of one or multiple hormones from the pituitary glands

Question 62

Hypopituitarism is a lower or lack of secretion/synthesis of one or multiple hormones from the pituitary glands. What are the 3 main causes?

Answer 62

1 - tumour 2 - infection 3 - vascular failure

Question 63

Cushings syndrome can cause severe muscle, bone and skin breakdown and soreness. Why is this?

Answer 63

- muscle, bone and skin are main sites of protein storage - elevated cortisol causes proteolysis as a source of energy - small amounts are good in acute stress response, but chronic can be bad

Question 64

Cushings syndrome can cause central adiposity. Why is this?

Answer 64

- cortisol increases gluconeogenesis, increasing blood glucose levels - insulin secretion is increased, preferentially storing glucose in adipocytes - specifically adipocytes in central region are targetted