Hypothalamic-pituitary axis

Question 1

The endocrine system

Answer 1

A complex interactive system
One of the main communication systems of the body
Intimately involved in homeostatic control of many bodiky functions

Question 2

Endocrine hierarchy

Answer 2

Hypothalamus (conductor) > pituitary (leader) >peripheral endocrine system

Question 3

Feedback control

Answer 3

Hormones act via negative feedback to both the hypothalamus and the pituitary.

Question 4

The pituitaty gland

Answer 4

Small gland
Located at the base of the brain
Attached to the hypothalamus
Two distinct parts with different embryological origins
Posterior pituitary
Anterior pituitary

Question 5

Posterior pituitary

Answer 5

The hypothalamus, pituitary stalk and posterior pituitary are all derived from a downgrowth of the developing brain.
More about this in posterior piyuitary flashcards.

Question 6

Anterior pituitary

Answer 6

Arises from an upgrowth of the pharynx
Has vascular but not neural connections with the hypothalamus.
Controlled by hypophysiotrophic hormones from the hypothalamus.

Question 7

Anterior / intermediate pituitary Hormones

Answer 7

LH
FSH
TSH
GH
PRL
ACTH
MSH

Question 8

LH - lutenising hormone

Answer 8

In females it induces ovulation and formation of the corpous luteum, stimulating steroid synthesis.
In males it stimulates testosterone synthesis.
Secreted by basophils.

Question 9

FSH -Follicle stimulating hormone

Answer 9

Induces follicular development in the female
Involved in spermatogenesis in the male
Secreted by basophils

Question 10

TSH - thyroid stimulating hormone

Answer 10

Stimulates tri-iodothyronine (T3) and thyroxine (T4) synthesis.
Stimulates growth of the thyroid.
Secreted by basophils

Question 11

GH - growth hormone

Answer 11

Stimulates growth of the long bones
Increases protein synthesis
Raises blood glucose level (diabetogenic)
Acts on liver and other tissues to release somatomedins (insulin like growth factors)
Synthesised and released from acidophils

Question 12

PRL - prolactin

Answer 12

Induces growth of mammary tissue and increases milk production
Synthesised and released from acidophils

Question 13

ACTH - adrenocorticotrophic hormone

Answer 13

Increases the synthesis and release of glucocorticoids from the adrenal cortex

Question 14

MSH

Answer 14

Stimulates melanocytes to produce melanin leading to darkening of the skin

Question 15

Hypothalamic-pituitary portal system

Answer 15

Neurosecretory neurones secrete hormones into this, these. Are then transported to the anterior pituitary. Each hormone of the anterior pituitary is controlled by hypothalamic secretions.

Question 16

Hyperprolactinaemia

Answer 16

Caused hy a pituitary tumour
Increases prolactin secretion
Causes breast development in males
Infertility in males and females
Inhibits FSH and LH release
Treatment by D2 receptor agonist such as bromocryptine

Question 17

Pituitary tumours

Answer 17

Cause increased GH release (acromegaly)
Increased growthin long bones
Treated with somatostatin analogues such as octreotide.

Question 18

Hyposecretion

Answer 18

Can be due to trauma such as stroke.
Pituitary dwarfism caused by too little GH, treatment is HRT (GH given in growth phase)
GH can be genetically engineered

Question 19

Testing for adrena insufficientcy

Answer 19

If exogenous ACTH increases cortisol output from the adrenals this is an indication that the adrenals are functining normally and the problem is at a pituitary level. If there is no adrenal respinse then this is an indication that the adrenals are underfunctioning.