ChemPath: Pituitary Flashcards
Why doesn’t hypopituitarism cause low blood pressure?
The adrenals are still able to produce aldosterone
Which hypothalamic hormones affect prolactin release?
Dopamine → negative
TRH → positive
NOTE: hypothyroidism causes hyperprolactinaemia
How might pituitary failure present in women?
Amenorrhoea and galactorrhoea
What physical manifestation might a macroadenoma of the pituitary gland (>1cm) cause?
Bitemporal hemianopia
NOTE: this can be tested using a visual field test
What is the main problem with prolactinomas?
It might reduce/stop the production of other pituitary hormones (e.g. FSH and LH) or affect the axis
High prolactin in itself is not much of an issue.
What is the CPFT?
Combined Rapid Anterior Pituitary Evaluation Panel
Test for pituitary function
Which three stimuli of pituitary hormone secretion are used in the CPFT?
- Hypoglycaemia - increases CRH/ACTH and increases GHRH/GH
- TRH - increases TSH and prolactin
- LHRH - increases LH and FSH
What safety precautions must you take before subjecting a patient to hypoglycaemia?
- No cardiac risk factors (needs a normal ECG)
- No history of epilepsy
- Ensure good IV access
Describe the manifestations of increasing hypoglycaemia?
- Initially, the activation of the sympathetic nervous system will result in sweating, tachycardiac etc.
- When the blood glucose reaches <1.5mM, neuroglycopaenia may occur (loss of consciousness and confusion)
What blood glucose concentration is normally required to stimulate the pituitary gland?
<2.2mM
How should a patient be rescued if they experience severe hypoglycaemia during this CPFT?
50ml 20% dextrose
How much insulin should a patient with severe hypoglycaemia during a CPFT test receive?
0.15 U/kg
Outline the dosing of various drugs in the CPFT.
- 5mL syringe
- Insulin (0.15 U/kg)
- TRH 200 µg
- LHRH 100 µg
NOTE: the patient may experience a warm flush and vomit when the drug is administered
What should be measured in the blood?
- Glucose
- Cortisol
- GH
- LH and FSH
- TSH
- Prolactin
How frequently should hormone levels in the blood be measured?
- Every 30 mins for 60 mins - LH, FSH, TSH, prolactin
- Every 30 mins for 120 mins - glucose, GH, cortisol