L15 - The Hypothalamic Pituitary Axis

Question 1

The pituitary gland is situated within the sphenoid bone of the skull in a socket called?

Answer 1

The sella turcica

Question 2

Which part of the pituitary gland is a continuation of the same tissue as the hypothalamus?

Answer 2

Posterior

Question 3

What links the hypothalamus and the posterior pituitary?

Answer 3

The infundinulum (pituitary stalk)

Question 4

What are the embryological origins of each of the anterior and posterior pituitary gland?

Answer 4

Anterior - Rathke’s pouch

Posterior - neuroectoderm

Question 5

What two hormones are made in the supraoptic and paraventricular nuclei of the hypothalamus which are subsequently sent via neurocrine signalling to the posterior pituitary for storage and release?

Answer 5

Oxytocin and ADH

Question 6

What connects the hypothalamus and the anterior pituitary?

Answer 6

The hypophyseal portal system - I.e. release of one hormone from the hypothalamus induces another hormone from anterior pituitary

Question 7

What are the functions of oxytocin and ADH

Answer 7

Oxytocin - let down of milk and contraction of uterus during birth

ADH - regulation of body water volume

Question 8

What are the 6 tropic hormones released by the hypothalamus? These travel via the portal system to induce further hormones from the anterior pituitary

Answer 8

• Thryrotropin releasing hormone (TRH)
• prolactin release-inhibiting hormone (Dopamine)
• corticotropin releasing hormone (CRH)
• gonadotropin releasing hormone (GnRH)
• growth hormone releasing hormone (GHRH)
• growth hormone inhibiting hormone (somatostatin)

(Abbreviations are sufficient)

Question 9

What hormones does GnHR control the release of?

Answer 9

LH and FSH

Question 10

What is the effect of prolactin on the body?

Answer 10

To stimulate milk secretin and breast growth

Question 11

Using the flow chart on the wall to check name all the anterior pituitary hormones and their peripheral effects

Answer 11

Wall

Question 12

Be able to draw the three loops in the negative feedback of thyroid hormone as an example

Answer 12

Slide

Question 13

Cortisol is the stress hormone, describe some effects it can have on the body in excess levels

Answer 13

Hyperglycaemia, fat restriction, proteolysis, hypertension, anti-inflam, anti-stress

Question 14

What factors does growth hormone exert most of its effects via?

Answer 14

IGF’s

Question 15

GH stimulates growth of which category of bones both length (Before epiphyseal closure) and width (after epiphyseal closure) ways?

Answer 15

Long bones

Question 16

What is the function of GH and IGF’s in the adult?

Answer 16

Maintain RBC’s of bone and muscle mass and also to promote tissue repair

Question 17

Name some factors that stimulate growth hormone release and some that inhibit it

Answer 17

Stimulate - GHRH/deep sleep/stress/exercise/fasting (decrease in glucose)/dopamine
Inhibition - somatostatin/REM sleep/increase in glucose /obesity

Question 18

What does growth hormone deficiency cause if it occurs in childhood?

Answer 18

Pituitary dwarfism - very small stature, delayed or absent sexual development in teen years

Note - responds to GH therapy

Question 19

What could cause a growth hormone deficiency in a child?

Answer 19

Trauma during birth damaging the pituitary gland

Question 20

What does excess GH cause if it occurs in childhood and what is the most common cause of this?

Answer 20

Gigantism

Normally caused by a pituitary adenoma

Question 21

What does excess growth hormone cause if it occurs due to a pituitary adenoma in the adult? Give some symptoms

Answer 21

Acromegaly

Large hands feet and jaw

Question 22

Growth hormone can cause its effects directly through its receptor or via IGFR’s. Describe the GH receptor

Answer 22

It’s an RTK that is intrinsically linked to JAKs. Cross phosphorylation on these activates signalling pathways which cause growth and IGF production

Question 23

Which IGF is most prominent in feral growth?

Answer 23

IGF 2, IGF 1 is the major one in adults

Question 24

What does IGF modulate to cause growth?

Answer 24

Hypertrophy, hyperplasia, increase rate of protein synthesis, increased lipolysis in adipose tissue