Pituitary physiology and pathology Flashcards
(28 cards)
Which hormones are secreted from the anterior pituitary?
ACTH
TSH
LH/FSH
Growth hormone
Prolactin
Which two hormones are stored in the posterior pituitary?
Oxytosin
Vasopressin
How might a non-functioning adenoma present?
Temporal hemanopia - compression of the optic chiasm
Aquired squint - compression of cranial nerves 3, 4 or 6 causing extraocular muscle weakness
Hypoadrenalism
Hypothyroidism
Hypogonadism
(Diabetes Insipidus)
GH deficiency
What test can be performed if diabetes insipidus is suspected?
Water deprivation test
What are the physiological reasons for raised prolactin?
Breastfeeding
Pregnancy
Stress
Sleep
Which hormone, secreted from the hypothalamus, inhibits the secretion of prolactin?
Dopamine
What drugs can cause raised prolactin?
Dopamine antagonists e.g. metoclopramide
Antipsychotics e.g. phenothiazines
Antidepressants e.g. TCA
Other e.g. estrogens, coccaine
What are the pathological causes of prolactinoma?
Hypothyroidism
Stalk lesion e.g. RTA, iatrogenic
Prolactinoma
How might high prolactin present in females?
Galactorrhoea - 30-80%
Menstrual irregularity
Ammenorrhoea
Infertility
How might raised prolactin present in males?
Galactorrhoea - <30%
Visual field abnormal
Headache
Impotence
Anterior pituitary malfunction
Which gender tends to present early with raised prolactin?
Females
What investigations should be done if raised prolactin suspected?
Prolactin concentration
MRI Pituitary
Visual Fields - bitemporal hemanopia
Pituitary Function tests - ?other hormones affected
What features should be looked for on MRI of the pituitary in raised prolactin?
Microprolactinoma (<1cm)
Macroprolactinoma (>1cm)
Pituitary Stalk
Optic Chiasma
How is raised prolactin treated?
Dopamine agonists:
Bromocriptine
Quinagolide (norprolac)
Cabergoline (Dostinex)
Which dopamine agonist has the fewest side effects?
Cabergoline
What is acromegaly?
Excess of growth hormone
How might acromegaly present before epiphyseal fusion?
Giantism
What are the complications of acromegaly that might present?
Thickened soft tissues - skin, large jaw, sweaty, large hands
Hypertension
Cardiac failure
Headaches (vascular)
Snoring/Sleep apnoea
Diabetes mellitus
Local pituitary effects - visual fields, hypopituitarism
Early CV Death
How is acromegaly diagnosed?
Insulin-like growth factor 1 (IGF1) is measured and compared to normal values for age and sex
Glucose tolerance test - GH should suppress to <0.4ug/l after glucose
There is no suppression in acromegaly or fails to suppress below 1ug/l
What is the treatment for acromegaly?
Pituitary surgery
External radiotherapy to pituitary fossa
Retest GTT:
–GH <0.4ug/l = clinically satisfactory
–GH >1ug/l = needs drug therapy
Dopamine Agonist e.g. Cabergoline
Octreotide
Pegvisomant
What is the most common functioning pituitary adenoma?
Prolactinoma
What are the causes of pituitary hypofunction?
Primary or metastatic tumours
Traumatic brain injury
Subarachnoid haemorrhage
Infarction
Surgery or radiation
Granulomatous inflammation – sarcoidosis, tuberculous meningitis
Vascular diseases e.g. arteritis
Hypothalamic diseases e.g. syphillis
How can Cushing’s disease be distinguished from obesity?
Thin Skin
Proximal myopathy
Frontal balding in women
Conjunctival oedema (chemosis)
Osteoporosis
How can a pituitary pathology causing Cushing’s disease be distinguished from an adrenal pathology causing Cushing’s?
ACTH levels will be high in pituitary abnormality compared to very low in adrenal abnormality
