Acute Oncology Guidelines
- Routine monitoring for hypophysitis is not indicated, but there should be a high index of suspicion. If lymphocytic hypophysitis is suspected, U&Es, TSH, T4 and a random cortisol should be measured in the first instance (where possibly in an early morning sample, but this is not essential).
- If there is a high index of suspicion of lymphocytic hypohysitis, commence hydrocortisone 20mg mane; 10mg at 6pm; intravenous hydrocortisone 100mg 6hrly should be given if the patient is very unwell.
- All cases of suspected lymphocytic hypophysitis should be discussed with an endocrinologist.
- Interpretation of the random cortisol levels can be tricky. A cortisol level of >430 nmol/l is normal. Levels below this may be normal depending on the sampling circumstances and whether the patient is receiving steroids. A short synacthen test (SST) may be falsely normal in acute lymphocytic hypophysitis, but is a useful test if the hypophysitis is more longstanding (several weeks duration). Ideally a SST should be performed prior to initiation of hydrocortisone, but this may not be practically possible and it is better to start the hydrocortisone than unnecessarily delay treatment.
- Remember that TSH may be inappropriately low or ‘normal’ in hypothyroidism of pituitary origin, so T4 is the key measure.
- Thirst, polyuria and polydipsia may be indicative of diabetes insipidus, but diabetes mellitus and hypercalcaemia should be excluded.
- If lymphocytic hypophysitis is suspected on the initial blood screen, further hormone investigation can be co-ordinated by endocrinology and may include LH, FSH, testosterone (in men) and prolactin. A pituitary MRI will be required to exclude hypopituitarism secondary to a pituitary metastasis and to determine if there is any threat to the optic chiasm.
- Some oncology protocols recommend high dose dexamethasone if lymphocytic hypophysitis. There are no convincing data that this alters the natural history, i.e. reduces the likelihood of long-term pituitary dysfunction. However, if there is a significant inflammatory mass that is causing headache and/or visual disturbance then high dose dexamethasone should be commenced, but early discussion with an endocrinologist is recommended.
Hypophysitis
Immunotherapy can activate an autoimmune, inflammatory process within the thyroid – lymphocytic hypophysitis. This can cause hypopituitarism, which may in turn result in hypoadrenalism. The symptoms are non-specific but include:
- fatigue
- postural dizziness
- weight gain
- low mood
- headache
- visual field disturbance (rare)
- thirst, poluyuria, polydipsia.
Dilutional hyponatraemia/syndrome of inappropriate antidiuretic hormone secretion (SIADH) may be caused by cortisol deficiency; therefore hypophysitis should always be considered in any patient with hyponatraemia.