Pituitary Disease Flashcards
Where is the pituitary gland situated?
At the bottom of the brain as a protrusion of the hypothalamus.
At end of the infundibulum.
In the hypophyseal fossa of the sphenoid bone in a bony cavity called the sella turcica.
What is the other names for the anterior and posterior pituitary?
Anterior: Adenohypophysis
Posterior: Neurohypophysis
How does the hypothalamus communicate with the pituitary gland?
Via the hypothalamus-hypophyseal portal system to the anterior pituitary.
Nerves via the infundibulum to the posterior pituitary.
What does the anterior pituitary secrete?
ACTH GH TSH FSH/LH Prolactin
What does the posterior pituitary secrete?
ADH
Oxytocin
Summarises ADH regulation of water balance.
Insufficient water in body causes blood osmolality to increase.
This is sensed by osmoreceptors on the hypothalamus.
This causes ADH release from the posterior pituitary, which acts on the kidney to decrease free water excretion by reabsorbing water in the collecting duct.
Why is vision affected in some pituitary tumors?
As the optic chasm is located superiorly to the pituitary.
Growth of a tumor can compress the optic chiasm.
What is the most common visual defect caused by a pituitary tumor?
Bitemporal hemianopia.
What does hypopituarism mean?
Failure of the anterior pituitary function.
Can affect a single hormone or all hormones.
What can cause hypopituitarism?
- Tumours
- Previous radiotherapy
- Infarction/haemorhhage (apoplexy): e.g. Past-partum haemorrhage (Sheehans syndrome).
- Infiltration: e.g. sarcoid
- Trauma
What replacement therapy would be given for an ACTH deficiency?
Hydrocortisone
What replacement therapy would be given for a TSH deficiency?
Thyroxine
What replacement therapy would be given for a FSH/LH deficiency?
Testosterone (males) or Oestrogen (females)
What replacement therapy would be given for a GH deficiency?
Growth hormone
What replacement therapy would be given for a prolactin deficiency?
None
List causes of high prolactin?
- Prolactinoma
- Physiological: lactation, pregnancy
- Drugs that block dopamine e.g anti-psychotics, anti-emetics and tricyclines.
- ‘stalk effect’: When a tumor blocks the pituitary stalk and dopamine can’t reach the posterior pituitary to inhibit prolactin production.
What is the most common type of pituitary tumor?
Non-functioning pituitary - 25% of all.
What problems can non-functioning pituitary tumors cause?
- visual field defects
- headache
- can stop pituitary hormones working
- if big enough can interfere with cranial nerves causing eye movement problems.
What is a prolactinoma?
A pituitary tumor secreting prolactin.
What is classed as a micro and macro prolactinoma?
micro: <1cm
macro: >1cm
What symptoms does a promlactinoma cause?
- Galatorrhoea
- Headaches
- Visual field defect
- Amenorrhoea
- Erectile Dysfunction
- Mass effect
How do you diagnose a prolactinoma?
- Serum prolactin high: >6000
- MRI pituitary
- Test remaining pituitary such as gonadal function and thyroid hormones most affected.
How do you treat a prolactinoma?
- Dopamine agonists: Carbegoline/Bromocriptine/Quinagolide
- Surgery: Usually only if visual fields are compromised or medical therapy fails.
What problems are present with prolactinomas and pregnancy?
- Pituitary gets better in pregnancy
- Dopamine agonists are contra-indicated in pregnancy
- Cant do serial MRI’s to monitor
What pituitary tumor causing Agromegaly?
One that secretes GH.
How does acromegaly differ in adults and children?
Pre-puberty: Get giantism as growth plates haven’t fused yet so bones continue to grow.
Post-puberty: Get soft tissue enlargement but no increase in height. Instead get large jaw, hands and feet.
What are the symptoms of Agromegaly?
- Sweats
- Headaches
- Altered facial features
- Visual impairment
- Increased inter-dental space
- Cardiomyopathy
How is acromegaly diagnosed?
- Glucose tolerance test (as glucose normally supresses GH).
- Can measure IGF-1 (as GH stimulates the liver. Has a long half-life so is more useful than a random GH measurement.
What is the treatment for agromegaly?
Surgery: Can be fully removed or de-bulked.
Drugs:
- Somatostatin analogue e.g. Octreotide
- Dopamine agonist
- GH receptor agonist
Radiotherapy: for residual tumor or if on-going.
What gene is involved in acromegaly?
AIP gene
What is Cushing’s disease and Cushing’s syndrome?
A pituitary tumor is releasing ACTH is Cushings disease.
This is one of the causes of Cushings Syndrome.
What are the symptoms of Cushing’s disease?
- Cataracts
- Moon face with plethoric cheeks
- Increased abdominal fat
- Muscle wasting in arms and legs
- Buffalo hump
- Easy bruising
- Hypertension
- Thin skin
How is Cushing’s diagnosed?
Dexamethasone Suppression Testing
- High dose of steroid should switch off our cortisol production.
What is the treatment of Cushing’s?
Surgery as standard.
If surgery fails …
- Bilateral adrenalectomy
- Medical therapy: ketoconazole/metyrapone (blocks cortisol biosynthesis by inhibiting 11B-hydroxylase).
- Radiotherapy
What is a TSHoma?
A pituitary tumor releasing TSH.
What blood results are seen in a TSHoma?
Causes high TSH and high free T4.
What is diabetes insipidus?
Large amounts of dilute urine and increased urine.
What are the types of diabetes insipidus?
Central: due to lack of ADH caused by hypothalamus or pituitary.
Nephrogenic: Kidneys don’t respond to ADH.
What are the clinical features of diabetes insipidus?
Polydipsia: excessive thirst and excessive fluid intake.
Polyuria: urine output >3L/day.
What are the causes of diabetes insipidus?
- Trauma
- Pregnancy
- Pituitary tumor
- Familial
How is diabetes insipidus diagnosed?
Water deprivation test to try stimulate ADH release to assess ability to concentrate urine with ADH.
What is the treatment of diabetes insipidus?
Treat underlying cause.
DDAVP (desmopressin): spray, tablets or injection. This stops urination as frequently.
How is the pituitary accessed for surgery?
Trans-sphenoidal route.
