the pituitary gland - non functioning pituitary adenomas, hypopituitarism and cushings disease Flashcards
what are non functioning pituitary adenomas (NFPAs), what do they present with and how can they be treated?
Biochemically inactive tumours. Histologically, may have positive staining for native LH and FSH but don’t secrete active hormones.
present with visual field loss, headache or hypopituitarism
surgery is indicated if there is visual field defect or threat to vision
usual route is transphenoidal, although trans cranial surgery is occasionally needed
what causes hypopituitarism?
may be congenital or acquired
acquired is usually due to a pituitary tumour
other causes include
- inflammatory and infiltrative disorders (e.g diabetes insipidus)
- traumatic brain injury
- radiotherapy
what are the symptoms for hypopituitarism?
non specific symptoms e.g
- lethargy
- weight gain
- sexual dysfunction
- short stature in children
may present as an acute hypo adrenal crisis, with hyponatraemia and hypotension = medical emergency.
what are the investigations for hypopituitarism?
- need to exclude adrenal insufficiency
- confirm secondary hypothyroidism with low T4 and non elevated TSH
- confirm secondary hypogonadism with low sex hormones and non elevated LH and FSH
- post menopausal females, LH and FSH are good for screening for hypopituitarism and gonadotrophin should be elevated at this age
- GH deficiency is suggested by low IGF 1 levels
- MRI may show empty fossa or pituitary tumour
what is the treatment for hypopituitarism, including
- ACTH deficiency
- TSH deficiency
- gonadotropin deficiency
- GH deficiency
- ACTH deficiency treated with hydrocortisone
- TSH deficiency treated with thyroxine, with doses titrated according to symptomatic improvement and fT4 levels
- gonadotropin deficiency in men is treated with testosterone for symptom control and protection from osteoporosis (given as gel or injection)
- gonadotropin deficiency in women is treated with oestrogen and progesterone, given as the combined pill or HRT
- growth hormone deficiency in adults is treated with GH sub cut injections daily
what are the consequences of GH deficiency in adults?
can reduce QoL
reduced muscle and bone mass
increased fat mass with adverse cardiovascular profiles
what is Cushing syndromes characterised by?
- central obesity
- dorso-cervical fat pad (buffalo hump)
- increased roundness of face
- red face (plethora)
- thin skin
- easy bruising
- proximal myopathy
- hypertension
- premature osteoporosis
- DM
- thin skin
- red/purple striae
what investigations are done into cushings disease?
screening tests
- alcoholism
- depression
these conditions may cause patients to look cushingoid (pseudochushings)
- 24 hour urine free cortisol (will be elevated)
- Low dose dexamethasone suppression test (failure to suppress cortisol suggests cushings)
- overnight dexamethasone suppression test
- elevated late night salivary cortisol levels are a new outpatient test
what is the difference between cushings syndrome and cushings disease?
Any condition that causes the adrenal gland to produce excessive cortisol results in the disorder Cushing’s syndrome.
When a pituitary tumour secretes excessive ACTH, the disorder resulting from this specific form of Cushing’s syndrome is referred to as Cushing’s disease.
what are your differential diagnosis from cushings syndrome?
3 potential causes
- pituitary. ACTH is high or normal.
- adrenal. Hirsutism may suggest an adrenal tumour. If ACTH is low, suggests adrenal tumour due to negative feedback ACTH suppression by high cortisol levels.
- ectopic. hypokalaemia, smoking and weight loss are suggestive due to lung cancer or another malignancy. ACTH is high or normal
what investigations can be done to find the cause of cushings syndrome?
3 potential cause
- pituitary
- adrenal
- ectopic
so
CRH Test = CRH causes exaggerated rise in ACTH and cortisol in cushings disease, with flat response in ectopic ACTH.
ACTH is high in pituitary and ectopic causes, but low in adrenal cause.
smokings and hypokalaemia can suggests ectopic due to lung cancer or another malignancy.
High dose DST causes cortisol suppression in bushings disease but not ectopic
MRI of pituitary if there is a suggestive pituitary cause
Inferior petrosal sinus sampling (IPSS) may help confirm central ACTH secretion compared to periphery after CRH injection.
suspected ectopic, whole body CT scan and PET may reveal carcinoma elsewhere, often in the thorax.
what is Inferior petrosal sinus sampling?
an invasive procedure in which adrenocorticotropic hormone (ACTH) levels are sampled from the veins that drain the pituitary gland; these levels are then compared with the ACTH levels in the peripheral blood to determine whether a pituitary tumour is present.
uses the internal jugular vein
how is cushings syndrome managed?
- adrenal tumour = laparoscopic adrenalectomy
- ectopic ACTH, treat underlying malignancy and medically control cortisol
- cushings disease, trans sphenoidal removal of pituitary adenoma is indicated
- medical treatment with metyrapone and ketoconazole is possible
- radiotherapy may help
how does the overnight dexamethasone suppression test work?
dexamethasone is a synthetic glucocorticoid
patient takes before bed. Dexamethasone should interfere with negative feedback loop and lower ACTH levels, lowering cortisol levels.
However In someone with cushings this will not work and their cortisol and ACTH levels will still be high.
cortisol is measured but an ACTH test may be done as well
