Pituitary Endocrinology

Question 1

How is the pituitary gland connected to the hypothalamus?

Answer 1

By the infundibulum

Question 2

What are the lobes of the pituitary gland?

Answer 2

Anterior and posterior

Question 3

Through which blood vessels do hormones released from the hypothalamus reach the anterior pituitary gland?

Answer 3

Hypothalamo-hypophyseal portal vessels

Question 4

List each hypophysiotropic (hypothalamus) hormone and the hormone they induce the release of in the anterior pituitary.

Answer 4

Corticotropin releasing hormone = adrenocorticotropic hormone

Growth hormone releasing hormone = growth hormone

Thyrotropin releasing hormone = thyroid stimulating hormone

Gonadotropin releasing hormone = LH and FSH

Question 5

What is the benefit of hypothalamus hormones inducing the release of anterior pituitary hormones?

Answer 5

1. Permits negative feedback

2. Allows amplification of hypothalamic neurones into large hormonal signal

Question 6

Give the effects of each anterior pituitary hormone.

Answer 6

FSH & LH: Targets gonads to stimulate germ cell development. Stimulates release of progesterone and testosterone.

GH: Stimulates growth & protein synthesis

ACTH: Stimulates adrenal cortex to secrete cortisol

TSH: Stimulates thyroid to release T3 & T4 to increase metabolism

Prolactin: Stimulates breasts to produce milk

Question 7

Briefly describe how negative feedback works with the hormones CRH, ACTH and cortisol and why it is so important.

Answer 7

Stressful stimulus causes release of CRH then ACTH then cortisol. This leads to increased plasma cortisol levels. This feeds back to inhibit the CRH secreting neurones of the hypothalamus AND the ACTH secreting cells of the anterior pituitary. This prevents cortisol concentration increasing which prevents the damaging effects of excess cortisol.

The third hormone i.e. cortisol exerts the long loop negative feedback.

Question 8

What are the effects of tumours in the anterior pituitary gland?

Answer 8

1. Pressure on optic nerves, resulting in bi-temporal hemianopia
2. Results in excess release of pituitary hormones

Question 9

Are there neural connections in the anterior and posterior pituitary glands?

Answer 9

Anterior: No neural connections
Posterior: Originates from neural tissue + many glial cells

Question 10

Name 2 hormones the posterior pituitary gland synthesises.

Answer 10

ADH/vasopressin

Oxytocin

Question 11

How are the posterior pituitary hormones released into the blood?

Answer 11

Released by exocytosis

Question 12

What are the effects of ADH?

Answer 12

1. Retains water, creates concentrated urine and increased blood volume
2. Causes vasoconstriction to increase blood pressure

Question 13

What is ADH released in response to?

Answer 13

Decreased blood volume 
Trauma
Stress 
Increased blood CO2
Decreased blood CO2
Increased osmotic pressure of blood

Question 14

What are the effects of oxytocin?

Answer 14

1. Stimulates smooth muscle contraction of breasts for lactation
2. Stimulates contraction of uterine smooth muscles until baby is born
3. Promotes onset of labour

Question 15

What type of receptor do all pituitary and hypothalamic hormones act on?

Answer 15

G-protein coupled receptor