Endocrinology: Pathology - Pituitary disorders

Question 1

Structure of pituitary

Answer 1

Connected to hypothalamus via pituitary stalk containing axons extending from hypothalamus and rich venous plexus

Question 2

Two components of pituitary

Answer 2

Adenohypophysis (anterior pituitary)

Neurohypophysis (posterior pituitary)

Question 3

Major component of pituitary?

Answer 3

Adenohypophysis (80% of gland)

Question 4

Histology of adenohypophysis

Answer 4

Composed of epithelial cells derived embryologically from developing oral cavity

Question 5

Six cell types in adenohypophysis and the hormones produced by each

Answer 5

1. Somatotrophs: GH
2. Mammosomatotrophs: GH, PRL
3. Lactotrophs: PRL
4. Corticotrophs: ACTH, POMC, MSH
5. Thyrotrophs: MSH
6. Gonadotrophs: FSH, LH

Question 6

POMC

Answer 6

Pro-opiomelanocortin

Question 7

MSH

Answer 7

Melanocyte-stimulating hormone

Question 8

Histology of neurohypophysis

Answer 8

Consists of pituicytes (modified glial cells) and axonal processes extending from hypothalamus through pituitary stalk to posterior lobe (axon terminals)

Question 9

Describe the process of hormone production and release in the neurohypophysis

Answer 9

Peptide hormones synthesised in the hypothalamus and transported through axons to posterior pituitary, then released directly in response to appropriate stimuli

Question 10

Hormones released from the neurohypophysis

Answer 10

1. Oxytocin

2. Antidiuretic hormone (ADH; arginine vasopressin, AVP)

Question 11

Stimuli for oxytocin release

Answer 11

Dilation of cervix in pregnancy (oxytocin causes uterine smooth muscle contraction to facilitate parturition)
Nipple stimulation in postnatal period (oxytocin causes contraction of smooth muscles of lactiferous ducts of mammary glands to facilitate lactation)

Question 12

Stimuli for ADH release

Answer 12

Decreased BP detected by baroreceptors in cardiac atria and carotids (increased atrial distension inhibits ADH release)
Increased plasma osmotic pressure detected by osmoreceptors

Question 13

Causes of hyperpituitarism

Answer 13

1. Pituitary hyperplasia
2. Pituitary adenomas
3. Anterior pituitary carcinomas
4. Hormone secretion by non-pituitary tumours (e.g. paraneoplastic SIADH)
5. Certain hypothalamic disorders

Question 14

Most common cause of hyperpituitarism

Answer 14

Pituitary adenomas

Question 15

Causes of hypopituitarism

Answer 15

1. Ischaemic injury
2. Surgery
3. Radiation
4. Inflammatory disorders
5. Mass effect of non-functional pituitary adenomas