Pituitary Hypofunction Flashcards
Is it common for pituitary hypo function to affect specific hormones?
No
What is panhypopituitarism?
All the pituitary hormones are under secreted
What 5 things does panhypopituitarism result in?
- Hypothyroidism
- Hypoadrenalism
- Growth failure
- Hypogonadism
- Diabetes Insipidus
Name some causes of panhypopituitarism?
Tumours or metastases Infections Iatrogenic Granulomatous disease Vascular disease Trauma Autoimmune
What is Sheehan’s Syndrome?
This occurs during pregnancy when the pituitary gland enlarges and causes ischaemia of the gland
What are some signs and symptoms of hypogonadism?
Menstrual irregularities
Infertility
Impotence
Gynaecomastia
What are some general features of panhypopituitarism?
Abdominal obesity
Loss of facial, axillary and pubic hair
Dry skin and hair
What therapy is always given first in panhypopituitarism?
Hydrocortisone 10-25mg/day
Apart from hydrocortisone, what other hormone replacement therapies should be given in panhypopituitarism?
- Thyroxine 100-150mcg/day
- ADH desmospray nasal or tablets
- Nightly SC GH
- Sex hormone replacement
What is the sex hormone replacement therapy in females?
HRT/progesterone/oestrogen pill
What is the sex hormone replacement therapy in males?
Testosterone
What is the relationship between testosterone therapy and prostate cancer?
Testosterone therapy does not cause prostate cancer however it can enlarge the prostate and cause growth of a cancer if it is already there
What should always be done before starting testosterone therapy?
Screen for prostate cancer
What are two other side effects of testosterone therapy and how are they monitored?
Polycythaemia- monitor FBC
Hepatitis- monitor FBC
What is the only type of testosterone therapy that can causes hepatitis?
Oral
What are 4 effects of GH when given to adults?
- Improves wellbeing and quality of life
- Decreases abdominal fat
- Improves CV function
- Decreases cholesterol
What hormone mainly controls thirst and water regulation?
ADH
Where is ADH synthesised and where is it released?
Synthesised- hypothalamus
Released- posterior pituitary
Where is the predominant site of the action of ADH?
Kidneys
What receptors does ADH stimulate in the kidneys?
V2
What does ADH stimulating the V2 receptor do?
Allows the collecting ducts to become permeable to water via the migration of AQP2 channels, thus allowing reabsorption of fluid
What is the overall result of ADH secretion?
Decreased diuresis and overall retention of water
What other receptors does ADH target at high concentrations?
V1 in vascular tissues
What effect does ADH have when it binds with V1 receptors?
Vasoconstriction
What are changes in plasma osmolality sensed by?
Osmoreceptors in the anterior hypothalamus
At what osmolality is ADH secretion suppressed?
< 280
If plasma osmolality increases, what happens to the secretion of ADH?
Increases
What is nephrogenic DI?
The renal tubules are resistant to ADH (receptor abnormality)
What can cause nephrogenic DI?
Lithium, hypokalaemia, hypercalcaemia, genetics
What is cranial DI?
A problem secreting ADH from the posterior pituitary as a result of hypothalamic disease
What can cause cranial DI?
Tumours and metastases, granulomatous disease, trauma
How do you calculate serum osmolality?
2Na + 2K + glucose + urea
What is the normal range for serum osmolality?
285-295
What are the main clinical features of DI?
Polyuria and polydipsia
What is the most common cause of DI?
Hypothalamic-pituitary surgery
What happens when DI occurs following hypothalamic-pituitary surgery?
It is transient and usually remits after a few days-weeks
What is familial isolated vasopressin deficiency?
Causes DI from a young age and is dominantly inherited
What type of disease is Wolfram Syndrome?
Rare, autosomal recessive
What diseases does Wolfram Syndrome comprise?
DI, DM, optic atrophy, deafness
Where is the mutation that causes Wolfram Syndrome?
WFS1 gene on chromosome 4
What may an MRI show in Wolfram Syndrome?
An absent or poorly developed posterior pituitary
What will plasma and urine osmolality be in DI?
Plasma- high
Urine- low
What will the sodium concentration be in DI?
High
What will happen when there is fluid deprivation in DI?
The urine still will not concentrate
What is the main test for DI?
Water deprivation test
What would be a normal response following a water deprivation test?
Serum osmolality remains within the normal range
Urine osmolality > 600
What would be a DI response following a water deprivation test?
Serum osmolality rises above normal without adequate concentration of urine osmolality (serum > 300, urine < 600)
What type of DI is present if desmopressin still will not concentrate the urine?
Nephrogenic
What type of DI is present if desmopressin causes the urine osmolality to increase by 50%?
Cranial
What treatment options are there for DI?
- Nasal desmospray 10-60mcg/day
- Oral desmopressin tablets 100-1000mcg/day
- IM desmopressin injection 1-2mcg/day
What is syndrome of inappropriate ADH secretion?
Ectopic production of ADH
Name some causes of inappropriate ADH secretion?
Carcinoid tumours, pulmonary lesions, CNS damage, alcohol withdrawal, porphyria, drugs
What does inappropriate ADH secretion cause?
Retention of water and hyponatraemia
What is the presentation of inappropriate ADH secretion?
Usually vague, with confusion, nausea, irritability and later on fits and coma
What is the main treatment of inappropriate ADH secretion?
Treat the underlying cause
What is the most effective symptom relief for ectopic ADH production if patients can tolerate it?
Fluid restriction to 500-1000ml per day
What drug is used for ectopic ADH production if fluid restriction isn’t tolerated?
Demeclocycline
What drug can be used in the long run of inappropriate ADH secretion?
Vasopressin V2 antagonists
