The Pituitary Gland

Question 1

What are the two lobes of the pituitary gland?

Answer 1

Anterior
Posterior

Question 2

Where is the pituitary gland located?

Answer 2

Pituitary fossa, beneath the hypothalamus

Question 3

Anterior pituitary

Answer 3

Secrets hormones
Controlled by hormones secreted by the hypothalamus

Question 4

What controls hypothalamic hormone production?

Answer 4

Influenced by higher centres in the brain - neurotransmitters e.g. serotonin
Negative feedback from pituitary (short-loop) and target organ (long-loop)

Question 5

Structure of anterior pituitary hormones

Answer 5

Peptides/polypeptides: gH, prolactin, ACTH
Glycoproteins: TSH, FSH, LH composed of two glycoprotein chains (alpha and beta subunits)
All routinely measured by immunoassay

Question 6

Diseases caused by pituitary hypo/hyperfunction are known as _________________.

Answer 6

Secondary (secondary hyperthyroidism)

Question 7

Hormone deficiency caused by target organ

Answer 7

Primary (primary hyperthyroidism)

Question 8

Causes of pituitary and hypothalamic disorders

Answer 8

Tumours
Infection
Trauma

Question 9

Pituitary tumours can

Answer 9

Occupy space can cause headache, vomiting and visual field effects

Question 10

pituitary hypersecretion is usually associated with _____________ secreting the relevant hormone.

Answer 10

Benign adenomas

Question 11

The most common hormone produced by pituitary tumours is ______________.

Answer 11

Prolactin

Question 12

Hypopituitarism

Answer 12

Hypothalamic or pituitary disease
Most common cause is pituitary tumours

Question 13

What is pituitary apoplexy?

Answer 13

Haemorrhage into the pituitary, usually caused by a tumour. Sudden onset with signs of meningitis, visual problems, and loss of consciousness. Urgent treatment needed.

Question 14

How to investigate hypopituitarism?

Answer 14

Stim tests
Visual field examination
Skull radiography and imaging, CT or MRI

Question 15

What are three stim tests of hypopituitarism?

Answer 15

Insulin induced hypoglycaemia -> GH or cotisol (ACTH)
TRH -> TSH
GnRH -> LH or FSH

Question 16

3 steps in stim test

Answer 16

Measure basal
Add stimulus
Measure response

Question 17

Primary hypothyroidism thyroid function test

Answer 17

⬇️T4
⬆️TSH

Question 18

Secondary hypothyroidism thyroid function test

Answer 18

⬇️ T4
⬇️TSH

Question 19

Primary hyperthyroidism thyroid function test

Answer 19

⬆️T4
⬇️TSH

Question 20

Secondary hyperthyroidism thyroid function test

Answer 20

⬆️T4
⬆️TSH

Question 21

Explain the hypothalamic-pituitary-adrenal axis using Cushing’s syndrome as an example

Answer 21

Hypothalamus = CRH
Pituitary = ACTH
Adrenal gland = cortisol

Cushing’s syndrome - the adrenal glands produce an excess of cortisol.
due to adrenal tumours (primary)
due to excess secretion of ACTH by a pituitary tumour (secondary)
(secondary known as Cushing’s Disease, 60-70% of cases).

Hormone levels :
Primary Cushing’s Syndrome
⬆️ Cortisol,⬇️ ACTH

Secondary Cushing’s Syndrome
⬆️Cortisol, ⬆️ ACTH

Question 22

Growth hormone

Answer 22

Stimulates liver to produce insulin-like growth factor-I (IGF-I)
Increases lipolysis, liver glucose production and decreases tissue glucose uptake, increases protein synthesis

Question 23

Explain the effects of growth hormone (lengthy)

Answer 23

Excercise, sleeping and stress promote the CNS to release neurotransmitters which along with fasting, hypoglycaemia and arginine promote the hypothalamus to release GHRH. This can be inhibited by the action of hyperglycaemia. GHRH can stimulate the anterior pituitary to release growth hormone, somatostatin can inhibit this process. Growth hormone as well as having metabolic effects, acts on the liver to produce IGF-I which promotes anabolic growth.

Question 24

Two conditions of excess growth of soft tissues and bone

Answer 24

Gigantism
Acromegaly (adults)

Question 25

What test can we carry out to investigate raised GH?

Answer 25

OGTT (oral glucose tolerance test)

Question 26

Growth hormone deficiency

Answer 26

Congenital or acquired Rare Growth retardation in children

Question 27

Prolactin

Answer 27

Intimate and sustain lactation Controlled by hypothalamus through dopamine

Question 28

Hyperprolactinaemia

Answer 28

Prolactinoma - treated with dopamine agonists Anything that affects dopamine reaching the pituitary Hypothyroidism - TRH stimulates prolactin secretion Cause of infertility; impotence in males and menstrual irregularities in females

Question 29

What two hormones does the pituitary hormones secrete?

Answer 29

Arginine vasopressin/ anti-diuretic hormone Oxytocin

Question 30

Oxytocin

Answer 30

Controls uterus contractility and lactation - disorders of its release are not of clinical importance

Question 31

Deficiency of __________ action causes diabetes insipidus.

Answer 31

ADH

Question 32

Excess ADH secretion causes…..

Answer 32

SIADH

Question 33

What are the two main types of diabetes insipidus?

Answer 33

Cranial - failure of ADH secretion Nephrogenic - failure of kidney to respond to ADH

Question 34

Two rare types of diabetes insipidus

Answer 34

Dipsogenic -inappropriate excessive fluid intake Gestational - only occurs during pregnancy (an enzyme made by the placenta destroys ADH in the mother)

Question 35

How to confirm and differentiate DI diagnosis?

Answer 35

Diagnosis can be confirmed with a fluid deprivation test - in normal subjects urine will become concentrated and serum osmolality will not exceed 295 mmol/L. In diabetes insipidus urine will fail to concentrate and serum osmolality rises. Cranial and nephrogenic DI can be distinguished in a final stage of the fluid deprivation test - patients are given a synthetic analogue of ADH/vasopressin (desmopressin). In cranial DI the urine becomes concentrated but urine will remain dilute in those with nephrogenic DI whose kidneys are insensitive to ADH