Pituitary Disorders incl DI Flashcards
Clinical presentation of pituitary tumours
- pressure on surrounding structures > visual loss, headache, vomiting, nausea
- abnormality on pituitary function > hyper/hypo secretion
Reason for visual field loss in pituitary tumours
Upwards (superior) growth of pituitary tumour
Pressure on the optic chiasm
bitemporal haemianopia
Consequences of sideways (lateral) growth of pituitary tumour
Pain
Double vision
Consequences of upwards (superior) growth of pituitary tumour
Visual field loss due to pressure on optic chiasm causing bitemporal hemianopia
what is hypopituitarism?
What is it commonly caused by?
- diminished hormone secretion by the anterior pituitary gland (+ADH)
- pituitary adenoma
Changes in hormone levels in hypopituitarism
all go down apart from prolactin increase
due to disinhibition hyperprolactinaemia
What is the best imaging modality for pituitary gland?
MRI
what does Growth hormone deficiency cause?
Short stature in children - pituitary dwarfism
Reduced quality of life in adults
what does Gonadotropin (LH + FSH) deficiency cause?
- delayed puberty
- loss of secondary sexual characteristics in adults
- early sign: loss of periods
- lack of libido
- infertility + impotence
what does TSH deficiency cause?
Symptoms
Hypothyoidism
- low thyroid hormones
- weight gain
- fatigue
- bradycardia
- non elevated TSH
- low T4
- intolerance to cold
what does ACTH deficiency cause?
ACTH controls cortisol
- low cortisol
- tired
- dizziness
- hypotension
- hyponatraemia
Can be life threatening
What are the common hormones in excess in abnormalities in pituitary function?
- prolactin
- GH
- ACTH
What are the rare hormones in excess in abnormalities in pituitary function?
- TSH
- LH/FSH
What does HPA stand for
Hypothalamic-pituitary-adrenal
What do you do if you think a hormone is too low?
Stimulation test
What do you do if you think a hormone is in excess?
Suppression test
Adrenal axis tests
Deficiency- synacthen test, insulin stress test
Excess- dexamethasone suppression test
Who should an insulin stress test not be done on and why?
patients with ischaemic heart disease or epilepsy
risk of triggering coronary ischaemia or seizures respectively
GH axis tests
Deficiency: insulin stress test
Excess: glucose tolerance test
2 types of prolactin-secreting pituitary tumours
Large tumour = macro-adenoma (>1 cm)
Small tumour = micro-adenoma (<1 cm) (more common)
Outline micro-prolactinomas incl. symptoms
- most common pituitary tumours
- F>M
- <1cm
- presentation of menstrual disturbances (or hypogonadism in men), galactorrhoea, infertility
How can PCOS and micro-prolactinomas be distinguished
PCOS has:
- presence of androgenic symptoms
- less elevated prolactin levels
- absence of pituitary lesion on MRI
what is the most common cause of hyperprolactinaemia?
+ physiological causes
prolactinoma - pituitary adenoma that secretes prolactin
pregnancy
stress
Suckling
exercise
drugs
Causes of hyperprolactinaemia
- medications e.g. anti-emetics, antipsychotics
- PCOS
- prolactinoma
- non functioning adenoma causing compression of pituitary stalk
- pregnancy
- profound hypothyroidism (rare)
how does hypogonadism arise from hyperprolactinaemia?
- increased plasma prolactin
- higher levels of dopamine for negative feedback
- dopamine inhibits GnRH secretion
- inhibition of FSH + LH secretion
How are prolactinomas treated?
- dopamine agonists e.g. cabergoline, bromocriptine
- not operation
Ensure patient isn’t pregnant
What does dopamine inhibit?
Prolactin
What does prolactin inhibit?
Luteinising hormone
Ovulation and secretion of sex hormones
Symptoms on hyperprolactinaemia in women
- menstrual disturbance
- fertility problems - hypogondasim
- galactorrhea - excessive or inappropriate milk production
- gynecomastia - hard breast tissue
Symptoms of hyperprolactinaemia in men
- present later than women - no periods
- larger tumours
- low testosterone - hypogonadism
- ED
- may have mass symptoms e.g. visual loss
What is Acromegaly
What is it due to?
- Large extremities - Large hands and feet
- due to GH secreting pituitary adenoma in adults
Clinical features of acromegaly
- increased size of feet + hands
- coarser facial features over time
- chin protrusion
- widely spaced teeth
- frontal bossing of forehead
- enlargement of tongue + soft palate > snoring + sleep apnoea
- sweating, headaches, hypertension, DM
Complications of untreated acromegaly
- premature cardiovascular death
- irreversible changes in appearance
- increased risk of thyroid + bowel cancer
- hypertension
- diabetes
Investigations of acromegaly
- oral glucose tolerance test
- IGF-1 levels
- MRI to identify pituitary adenoma
Biochemical test to confirm acromegaly
- oral glucose tolerance test resulting in failure to suppress GH
- elevated IGF-1
Treatment of acromegaly
- Surgical removal of tumour
- Radiation therapy
- dopamine receptor agonists e.g. cabergoline
- somatostatin analogues e.g. octreotide
Drug treatment of acromegaly
- dopamine agonists e.g. cabergoline
- somatostatin analogues e.g. octerotide
outline monitoring of disease activity in acromegaly
- oral glucose tolerance test post-surgery to indicate persistent disease
- periodic colonoscopy due to increased colon cancer risk
- assessment for sleep apnoea, diabetes + cardiovascular disease due to increased risk
what causes Cushing’s disease
ACTH-secreting pituitary tumour
Changes in appearance in Cushing’s disease
- round pink face
- round abdomen
- thin skin
- bruises easily
- striae/stretch marks
- osteoporosis- thin bones
- high BP
-diabetes - skinny arms and legs
What is primary polydipsia?
When patient has normally functioning ADH but drinks excessive amounts of water > polyuria
What is Diabetes insipidus caused by?
- Cranial DI: ADH deficiency - in pituitary disease
- nephrogenic DI: ADH resistance in kidney - metabolic + electrolyte disturbance, renal disease or nephrotoxic drugs
Causes of cranial diabetes insipidus
- idiopathic
- brain surgery/tumour/infection
- damage to pituitary/hypothalamus gland
Causes of nephrogenic diabetes insipidus
- nephrotoxic medications e.g. lithium
- hypercalcaemia
- hypokalaemia
- PCOS
- renal disease
Presentation of diabetes insipidus
polyuria
polydipsia
dehydration
postural hypotension
Investigations + confirmation of diabetes insipidus
- high serum osmolality
- low urine osmolality
- high urine volume (>3L per 24 hours)
- U&Es
Diagnosis of diabetes insipidus
water deprivation test
Outline the water deprivation test / desmopressin stimulation test
- patient avoids all fluids for 8 hours before test
- urine osmolality is measured
- if low, desmopressin (synthetic ADH) is given
- urine osmolality measured over 24 hours after
Outline the results of water deprivation test
- primary polydipsia: high UO after deprivation
- Cranial DI: low UO after deprivation + high UO after desmopressin
- nephrogenic DI: low UO after depravation+ desmopressin
Consequences of untreated diabetes inspidus
- dehydration
- hypernatraemia
- reduced consciousness
- coma
- death
Management of cranial diabetes insipdius
- desmopressin (synthetic ADH)
- monitor serum sodium - risk of hyponatraemia
- investigate for pituitary disease
Management of nephrogenic diabetes insipidus
- treat underlying cause
- stop damaging drugs
- drink according to thirst
- thiazide diuretics
- NSAIDs
- low salt
- low protein diet
What organ produces IGFs?
Liver
outline the clinical approach of the investigation of a suspected pituitary tumour
- endocrine function assessment: hormone levels + biopsy of tumour w antibiotics for hormone
- visual field defects assessment
- MRI scan
what is hypopituitarism often due to?
pituitary adenoma > progressive loss of anterior pituitary function
what is panhypopoituitarism?
deficiency in all anterior pituitary hormones
What is hyperpituitarism?
What is it commonly caused by?
- Excess pituitary hormone production (prolactin, GH + ACTH)
- due to functional hypersecreting pituitary adenoma
What is a pituitary apoplexy
Bleeding into or impaired blood supply of the pituitary gland
Symptoms of pituitary apoplexy
Sudden onset headache
Double vision
Cardinal nerve palsy
Visual field loss
Hypopituitarism
What is the most common causes of pituitary disorders?
Describe this
Pituitary adenoma
- benign tumour
- often non functioning (do not produce any hormones) - have negative effect due to pressure exerted
What hormones are most commonly affected by Hypopituitarism?
- ACTH
- ADH
- TSH
- Growth hormone
- Gonadotrophin (LH/FSH)
What hormones are most commonly affected in hyperpituitarism?
Prolactin
Growth hormone
ACTH
What can a GH excess cause in childhood vs adulthood?
Childhood - gigantism
Adulthood - acromegaly
Why can growth hormones excess cause diabetes mellitus?
GH antagonises insulin
