Pituitary Gland lecture Flashcards
Location and relations
Base skull
Sella tursica
Attached to hyppthalamus via stalk
Cavernous sinuses either side
Optic chiasm superiorly
Size of pituitary
13mm x 9mm 100mg
When does pituitary size change?
- Doubles pregnancy
- Shrinks elderly
Blood supply to pituitary
- Hypothalamo-hypophyseal portal system
- Derived from superior and inferior hypophyseal arteries
Venous drainage of pituitary
- Through cavernous sinus into petrosal sinuses and internal jugular veins
Important to know this for venous sampling
What is produced by pituitary gland?
8 hormones
6 anterior - FSH, LH, GH, ACTH, TSH, Prolactin
2 posterior - ADH and oxytocin - just stores these, does not produce
What is hypopituitarism
Partial or complete deficiency of anterior and or posterior pituitary hormones
May be all hormones, partial or singular
Can be primary or secondary due to hypothalamus pathology
Causes of hypopituitarism
- Pituitary or parapituitary tumours eg meningioma, mets
- Radiotherapy
- Infarction - apoplexy, Sheehans
- Infiltration - sarcoidosis, lymphocytic, haemachromotosis
- Infection - eg TB/abscess
- Trauma or SAH
- Isolated deficiencies - Kallmanns
- Genetic
Clinical manifestations of hypopituitarism
- GH - short stature if occurs when under 18, reduced exercise capacity
- FSH/LH - amenorrhoea, anovulation, erectile dysfunction, reduced libido
- ACTH - hyperkalaemia, hypoadrenal crisis
- TSH - hypothyroidism
- PRL - failure lactation
- ADH - polyuria and polydipsia
Investigations for hypopituitarism
- Basal hormone levels (cortisol done at 9am when highest)
- Investigate cause - MRI, serum ACE (sarcoid), hCG, ferritin (haemochromatosis) AFP (tumours)
- Biopsy?
Dynamic testing for growth hormone
- Glucagon
- Arginine
- Insulin tolerance test
All try to stimulate glucagon production
Dynamic testing for ACTH
- Short synacthen test
- Also long - not really used now
Dynamic testing for FSH and LH
GnRH administration
Test for ADH deficiency
- Plasma and urine osmolarity
- Urine Na
- Fluid deprivation test - see if urine concentrates
Signs of hypersecretion of pituitary hormones
Acromegaly
Cushings
Most common brain tumour
Adenoma
Classification of pituitary tumours
- Size - macro vs micro
- Functional vs non-functional
Order of incidence of adenoma types
- Prolactinoma
- Non functioning - mass effect
- GH - acromegaly
- ACTH adenoma -Cushings disease
- TSH adenoma - RARE
Physiological causes of hyperprolactinaemia
- Pregnancy
- Breastfeeding
- Exercise
- Stress
- Sleep
- Seizure