Pituitary: Part1 Flashcards
Anatomy of Pituitary (4)
-hypothalamus
-optic chasm
-pituitary stalk
-pituitary
Pituitary Development: Anterior pituitary cell lineages (3)
Physiology of Pituitary
Pituitary Hormones (8)
ACTH
TSH
GH
PRL
FSH
LH
MSH
ADH
HPA axis (3)
Hypothalamic
Pituitary
Adrenal
axis
Prolactin regulation (3)
Prolactin is the major lactogenic hormone
Secreted from anterior pituitary
Under tonic inhibition by hypothalamic dopamine
Stored in hypothalamus (5)
-CRH
-TRH
-GnRH
-GHRH
-Dopamine
Stored in anterior pituitary (5)
Steroids= ACTH > Cortisol
Thyroid= TSH> Thyroxine
Sex hormones= LH/FSH> E2/Testosterone
Growth hormone= GH > IGF1
Prolcatin= PRL
Stored in posterior pituitary
-vasopressine
-oxytocin
Clinical implications of Pituitary Disease (4)
- TOO MUCH HORMONE
- TOO LITTLE HORMONE
- GLAND TOO BIG
Some Pituitary Tumours may be doing ALL THREE
Consequences of Pituitary Tumours/Enlargement (2)
Compression/impingement on optic chiasm – Visual field defect
Extension into cavernous sinus – Cranial Nerve Defects (III, IV, VI)
Sphenoid sinus
Compression of optic chiasm
bitemporal hemianopia
Assessment of pituitary function (2)
Baseline tests are sufficient but sometimes “dynamic tests” needed to get more information – especially on the steroid axis
Diurnal pattern to physiological hormone secretion (e.g. cortisol)
Principles of Dynamic Testing
IS THERE TOO MUCH HORMONE?
Do a test that tries to suppress the hormone
IS THERE TOO LITTLE HORMONE?
Do a test that tries to stimulate the hormone
Baseline Pituitary Function
9am cortisol
* TSH, Free thyroxine, Free T3
- Prolactin
- LH/FSH, oestradiol (F), 9am testosterone (M)
- NB: LH/FSH should be elevated in post-menopausal females
- IGF-1 (surrogate for growth hormone)
- Plasma/Urine osmolality
Baseline Anterior Pituitary Function
Pit-
*9am ACTH
*TSH
* LH/FSH
*GH
*Prolactin
Peripheral fucntion
*9am cortisol
*Thyroxine Free T4, Free T3
*9am Oestradiol (F), Testosterone (M)
* IGF-1 (surrogate for growth hormone)
Dynamic Pituitary Function Tests: HPA and GH= Synacthen
Synacthen (synthetic ACTH) Test: assessment HPA axis
Cortisol response to 250mcg synacthen:
Cortisol measured at: Baseline (0 mins)
-30 minutes
-60 minutes
Normal response: increment >150nmol/l AND peak cortisol >500-550nmol/l (assay dep.)
(caveat- may not be reliable in acute pituitary failure)
Dynamic Pituitary Function Tests: HPA and GH= Insulin Stress Test
Insulin Stress Test or Prolonged Glucagon Test: assessment of HPA and GH axes
Cortisol and GH response every 30 min for 2-3 hrs
Normal response:
Peak Cortisol >500nmol/l
Peak GH >7uh/l
Hypopituitarism
Pituitary Hormone Deficiency
Clinical features associated with anterior pituitary deficiency (5)
→Growth Hormone; Growth hormone deficiency (GHD)-growth failure
→ TSH; hypothyroidism (secondary)
→ LH/FSH; Hypogonadism (hypogonadropic hypogonadism)
→ ACTH; hypoadrenal (secondary)
→ Prolactin; none known
Clinical features associated with posterior pituitary deficiency
→ADH deficiency: Arginine vasopressin deficiency (diabetes insipidus)
Causes of Hypopituitarism (8)
- Non pituitary brain tumours :e.g. Craniopharyngioma, meningioma, glioma, chordoma, metastases (lung, breast)
- Brain injury/damage: e.g. trauma, subarachnoid haemorrhage
- Iatrogenic; e.g. pituitary surgery, irradiation
- Granulomatous disease & Hypophysitis: e.g. TB, Langerhan Cell Histiocytosis, Sarcoidosis, Lymphocytic Hypophysitis, haemochromatosis, medication (monoclonal antibodies)
- Vascular: e.g. pituitary apoplexy ; Sheehan’s syndrome
- Infection; meningitis, encephalitis, abscess
- Genetic/Hereditary
- Idiopathic
ACTH Deficiency (3)
-Chronic: fatigue, pallor, anorexia, weakness
- Acute: weakness, dizziness, nausea, vomiting, shock
- In children: delayed puberty, failure to thrive
