Anterior Pituatory

Question 1

What is the pituitary gland?

Answer 1

Secretes hormones in response to signals from hypothalamus

Weighs 0.5g
Pea sized

Question 2

Blood supply

Answer 2

Hormones are secreted into the portal system

The anterior pituitary has no arterial blood supply but receives blood through a portal venous ACTH circulation from the circulation from the
hypothalamus

Question 3

Anterior lobe secretes

Answer 3

ACTH
TSH
GH
LH
FSH
Prolactin

Question 4

Posterior lobe secretes

Answer 4

Vasopressin (AVP)

Oxytocin

Question 5

Anterior pituitary hormones

Answer 5

Table

Specificity of hormone is determined by different beta unit

Question 6

Hypothalamus function

Answer 6

Collection of brain ‘nuclei’

• Connections to almost all other areas of the brain

• Important for homeostasis + primitive functions – appetite, thirst, sleep, temperature regulation

• Control of autonomic function via brainstem autonomic centres

• Control of endocrine function via pituitary gland

Question 7

Hormone released by pituitary and releasing hormone by hypothalamus

Answer 7

Slide 12

Question 8

Negative feedback

Answer 8

Stress, cytokines and diurnal rhythm stimulate the hypothalamus

Slide 14

Only anterior pituitary hormone that doesn’t have negative feedback is prolactin

Question 9

Regulation of glucocorticoid levels

Answer 9

ACTH regulates glucocorticoid synthesis:
• Acutely stimulates cortisol release
• Stimulates corticosteroid synthesis (and capacity)
• CRH stimulates ACTH release
• Negative feedback of cortisol on CRH and ACTH production

Question 10

Cortisol circadian rhythm

Answer 10

Higher in the morning

Question 11

Growth hormone

Answer 11

Released throughout life Pulsatile
Stimulated by low glucose, exercise, sleep
Suppressed by hyperglycaemia Effects mediated by GH and IGF1

Question 12

Actions of growth hormone

Answer 12

Linear growth in children Acquisition of bone mass Stimulates: protein synthesis
lipolysis (fat breakdown) glucose metabolism
Regulation of body composition Psychological well-being

Question 13

Regulation of thyroid hormone levels

Answer 13

Negative feedback loop between TSH and thyroxine
In pituitary failure both TSH and thyroxine are low
(in a case of underactive thyroid, where thyroid and not pituitary is problem, thyroxine is low and TSH rises to stimulate thyroid)

Question 14

Female HPG axis

Answer 14

Involves hypothalamus, pitautary, gonads (ovaries)

Oestradiol stimulates

Question 15

LH/FSH

Answer 15

Essential for reproductive cycle
• LH stimulates sex hormone secretion
• FSH stimulates development of follicles
• Absence leads to infertility and hypogonadism

Question 16

Male HPG axis

Answer 16

Hypothalamus

Pitutaory

Goands

Question 17

Prolactin control

Answer 17

Synthesised in lactotrophs
• Regulation of PRL different to other anterior pituitary homones
– Negative regulation by tonic release in inhibiting factor - dopamine

Question 18

Prolactin

Answer 18

Essential for lactation
• Levels increase dramatically in pregnancy and
during breast-feeding – do not test at these times
• Inhibits gonadal activity through central suppression of GnRH (and thus decreased LH/FSH)
• Mainly causes disease when present in excess

Question 19

What do tumours cause?

Answer 19

1. Pressure on local structure e.g. optic nerves – Bitemporal hemianopia
2. Pressure on normal pituitary – hypopituitarism
3. Functioning tumour – Prolactinoma
   – Acromegaly
   – Cushing’s disease

Question 20

Pituitary hormone excess

Answer 20

ACTH – Leads to increased cortisol levels (Cushing’s disease)
• GH – Leads to increased GH and IGF-1 levels (Acromegaly)
• LH or FSH – Very rare! Might stop periods (Gonadotrophinoma)
• TSH – Leads to thyrotoxicosis. Very rare cause!
• Prolactin – Leads to galactorrhoea and amenorrhoea
• (Prolactinoma)