L2 - Intro to HPA axis

Question 1

What is the area directly above the pituitary gland

Answer 1

• Hypothalamus

Question 2

What is the pituitary gland connected to the brain via

Answer 2

• Infundibulum

Question 3

What is the pituitary gland divided into

Answer 3

• Anterior and posterior pituitary glands

- They effectively function independently

Question 4

What is the posterior pituitary gland sometimes called

Answer 4

• Is a ‘down growth’ from the brain

- It is sometimes called the neurohypophysis

Question 5

What are the hormones secreted by the posterior pituitary gland

Answer 5

• Antidiuretic hormone(ADH also called vasopressin)

- Oxytocin

Question 6

What type of hormones are ADH and oxytocin

Answer 6

• Peptide hormones

- Nine amino acids each, of which seven are identical

Question 7

Where are ADH and oxytocin produced

Answer 7

• Hormones are not synthesised within the gland, but are synthesised by the neurones of the hypothalamus
• Supraoptic nuclei and paraventricular nucleus
• These hormones are synthesised as inactive precursors and converted to active hormone within the posterior pituitary

Question 8

What are the inactive precursors of ADH and oxytocin transported via

Answer 8

• Transported from the supraoptic and paraventricular nuclei along the hypothalamico-neurohypophyseal tract
• They are then stored within the posterior pituitary

Question 9

What is secretion of ADH influenced by

Answer 9

• Plasma osmolarity

Question 10

What does stimulation of V2 receptors cause

Answer 10

• Stimulation of V2 receptors causes translocation of aquaporins to the membrane of the kidney tubule, thus allowing water reabsorption

Question 11

What does stimulation of v1 receptors cause

Answer 11

• Vasoconstriction

- This does not occur at physiological concentration

Question 12

What do disorders of ADH secretion lead to

Answer 12

• Disorders of fluid balance

Question 13

Effect of oxytocin

Answer 13

• Oxytocin acts via IP3 to cause contraction of the smooth muscle of the genital tract (uterus) and breast
• During parturition, oxytocin causes contraction of the smooth muscle of the uterus to aid expulsion of the infant
• Continued stimulation of the cervix causes continued secretion

Question 14

What is secretion of oxytocin stimulated by

Answer 14

• Stimulation of the genitals and nipples

Question 15

When is oxytocin most important

Answer 15

• At parturition and during lactation

Question 16

When does oxytocin synthesis increase

Answer 16

• During pregnancy, but there is a parallel increase in oxytocinase activity

Question 17

Is oxytocin necessary for initiation of normal labour

Answer 17

• Oxytocin is not necessary for the initiation of a normal labour
• But oxytocin may be administered to induce labour

Question 18

What is anterior pituitary gland also called

Answer 18

• An ‘up growth’ from the palate

Question 19

Hormones secreted by the anterior pituitary gland

Answer 19

• Growth hormone
• Prolactin
• Thyroid stimulating hormone
• Adrenocorticotrophic hormone
• Follicle stimulating hormone
• Luteinising hormone

Question 20

Which cells synthesise thyroid stimulating hormone

Answer 20

• Thyrotrophe cells

Question 21

Which cells synthesise adrenocrticotrophic hormone

Answer 21

• Corticotrophe cells

Question 22

Which cells produce follicle stimulating hormone

Answer 22

• Gonadotrophe cells

Question 23

Where are the releasing hormones secreted by the hypothalamus secreted into

Answer 23

• Hypothalamico-adenohypopyseal portal vessel which carries them to the anterior pituitary
• The releasing hormones do not enter the systemic circulation

Question 24

Biochemical tests that are part of clinical investigations

Answer 24

Start with Signs and Symptoms
Followed by
Biochemical Tests
(Basal Levels)

* TSH(not water soluble) & FT4(is free and therefore soluble)   
* Cortisol
* LH & FSH
* Prl
* Testosterone / “Periods”

Question 25

What is the test carried out after biochemical tests

Answer 25

- Imaging(eg MRI)

Question 26

Tests carried out after imaging

Answer 26

- Visual field tests | eg bilateral hemianopsia due to compression of optic chiasm

Question 27

Why is the timing of tests important

Answer 27

- Diurnal rhythms

Question 28

Why do you have to measure FT4 levels

Answer 28

- TSH is not biologically active

Question 29

Where is prolactin synthesised

Answer 29

- Is 199 amino acid peptide, synthesised in the lactotrophe cells of the anterior pituitary

Question 30

What is prolactin secretion controlled by

Answer 30

* The secretion of prolactin is under hypothalamic control by means of Prolactin Release Inhibiting Factor, which is DOPAMINE. * TRH stimulates prolactin synthesis.

Question 31

What is prolactin secretion stimulated by

Answer 31

- Mild stress - Nipple stimulation - Coitus

Question 32

Primary role of prolactin

Answer 32

- To promote lactation, and development of breast tissue - It is most important in females after puberty and during and after pregnancy - Prolactin is secreted in both males and females

Question 33

Where is growth hormone synthesised

Answer 33

• Growth hormone is synthesised in the somatotrophe cells of the anterior pituitary gland

Question 34

What is secretion of growth hormone secretion controlled by

Answer 34

• Secretion is controlled by the hypothalamus via - Growth Hormone Releasing Hormone (GHRH) and Growth Hormone Release Inhibiting Hormone (GHRIH, somatostatin). · Growth Hormone Releasing Hormone (GHRH) is more important in control than Growth Hormone Release Inhibiting Hormone (GHRIH, somatostatin).

Question 35

What can secretion of growth hormone be stimulated by

Answer 35

· Secretion of growth hormone is stimulated by decreased carbohydrates and fatty acids and increased amino acids.

Question 36

What can GH act via in some tissues

Answer 36

· In some tissues, GH acts via second messengers which are produced in the liver · Insulin-like growth factor 1 · Insulin-like growth factor 2

Question 37

What is the primary effect of GH

Answer 37

The primary effect of GH is to promote the linear growth of adolescence by increasing protein synthesis and collagen deposition This is mediated via the nucleus GH is also involved in tissue turnover and repair

Question 38

Effect of GH on foetal growth

Answer 38

Foetal growth is relatively independent of gH