The Pituitary Gland and its Disorders Flashcards
Describe the clinical signs and symptoms of pituitary tumours,
Hormone hypersecretion
Space occupying lesion- the tumour can compress on surrounding structures (esp the optic chiasm) and cause headaches, visual loss (field defect), or cavernous Sinus Invasion
Hormone deficiency states
Interference with surrounding normal pituitary
Anterior pituitary tumours can cause hormone hyper secretion. What are the various diseases associated with different excess hormones?
GH: Acromegaly ACTH: Cushings Disease TSH: Secondary thyrotoxicosis LH/FSH: (Non-functioning pituitary tumour) usually asymptomatic PRL: Prolactinoma
Describe Acromegaly
GH stimulates the liver to produce insulin GF1 (IGF-1). This acts on the chondrocytes to produce growth. Excess levels of this due to a pituitary tumour is called acromegaly, and has symptoms associated with excess growth
List some systemic effects of excess GH/Acromegaly
Acral enlargement: spade like hands, macroglossia (big tongue), carpal tunnel syndrome
Increased skin thickness, sweating, skin tags
Metabolic Changes: Impaired fasting glucose, DM Reduced total cholesterol Increased triglycerides Increased nitrogen retention
What is the role of prolactin and how is it controlled by positive feedback?
Dopamine from the hypothalamus stops the pituitary producing prolactin.
The reason for this is that prolactin is controlled by positive, not negative feedback.
During lactation, mechanical stimulation of the nipple sends a neural signal to the brain.
This stops dopamine production and there is a surge in PRL and milk so that the baby can be fed. PRL also inhibits LH and FSH
What are clinical features of prolactinomas?
Features of PRL excess: Infertility Amenorrhoea (periods stop) Galactorrhoea (lactating) Reduced libido Impotence
What are some causes of prolactinomas? How is PRL excess treated?
Many drugs interfere with DA and PRL secretion: Antiemetics Antipsychotics The pill Treatment: dopamine agonists
What are non-functioning pituitary tumours and how are these treated?
No syndrome of hormone excess produced
Cause symptoms due to space occupation
Treatment: surgery (transsphenoidal approach) ± radiotherapy
No effective medical therapy
What is the treatment of pituitary adenomas?
Surgery
Transsphenoidal
(Adrenalectomy - Nelson’s syndrome)
Radiotherapy
Drugs which block hormone production or stop Hormone Release
Give the causes of pituitary failure
Tumour Trauma Infection Inflammation: Sarcoidosis, Histiocytosis Iatrogenic- caused by medical treatment
What is Hypopituitarism? How is it treated?
Pituitary tumours which decrease pituitary hormone secretion, like cortisol, sex steroids, GH
Treated with hormone therapy- ie give the hormones which are deficient
What is syndrome of inappropriate ADH?
Aka SIADH
Too much ADH
Seen during brain injury/infection which secretes too much
Metabolic: Hypothyroidism, Addison’s (cortisol closes the aquaporins)
How would you diagnose and treat SIADH?
Low sodium, High urine osmolality Treatment Fluid restriction Demeclocyline ADH Antagonist (Tolvaptan)
What is diabetes insipidus?
Underproduction of ADH
This can be cranial- lack of Production from the hypothalamus
It can also be nephrogenic- receptor resistance in the kidney stops ADH effects
What is the water deprivation test and how can this be used to diagnose diabetes insipidus?
Prevent the patients water access for 8hrs, or until the patient has lost 3% of their body weight.
Normally, the urine would become conc and decrease in volume. But a DI patient would still have high volumes of urine.
After this we give an ADH injection (DDAVP). In a normal person the urine still remains concentrated. In DI, DDAVP makes the urine more conc and decreases its volume, and we know that it has a cranial cause.
If the ADH still makes no difference, then the cause of the DI is nephrogenic
