Pituitary function testing and histology Flashcards
How do clinical implications occur in pituitary disease?
Too much hormone secretion
Too little hormone secretion
Gland too big
What are baseline pituitary function tests?
These tests involve taking measurements of hormones as they are in the body, to understand whether there is too much or too little of a hormone
What are some examples of baseline pituitary function tests?
- 9am cortisol testing
- TSH, fT3/4
- Prolactin
- LH/FSH
- Oestradiol (F)
- 9am testosterone (M)
- IGF-1 (Surrogate for growth hormone)
- Plasma/Urine osmolarity
What are dynamic pituitary function tests?
These are tests in which hormone levels are suppressed or stimulated to show the whole hormone axis effect
What type of dynamic pituitary function test is required if there is too much of a hormone?
Suppression test
What type of dynamic pituitary function test is required if there is too little of a hormone?
Stimulation test
What are some examples of dynamic pituitary function tests?
Synacthen (Synthetic ACTH) test
Insulin stress test
Prolonged glucagon test
What is the purpose of a synacthen test?
This is to assess the HPA axis
How does a synacthen test work?
Chronic low ACTH will lead to adrenal atrophy, so the adrenal gland will not react to synthetic ACTH well if there is a pituitary gland problem with ACTH production
How is a synacthen test performed?
Synacthen is given and the cortisol levels are measured at 0 minutes, 30 minutes and 60 minutes
What is a normal and abnormal synacthen test result?
A normal response would be a cortisol level between 500 and 550
Chronic ACTH deficiency would show a cortisol level below 500
How does an insulin terms test work?
Insulin stress testing is a test in which hypoglycaemia is induced
This can be used to activate stress receptors in the hypothalamus and thus pituitary, leading to production of ACTH and GH
Cortisol and GH responses should then be measured every 30 minutes for 2-3 hours
What is a normal response to insulin stress test?
A normal cortisol response would be >500nmol/L
A normal peak GH would be > 7uh/l
What are the 3 types of cells of the pituitary gland?
Acidophils
Basophils
Chromophobes
What types of pituitary cells are acidophils?
Somatotrophs (GH)
Mammotrophs (Prolactin)
