The Pituitary Gland And Its Disorders Flashcards
What is another name for the anterior lobe of the pituitary gland?
Adenohypophysis
What is another name for the posterior lobe of the pituitary gland?
Neurohypophysis
What is the dual blood supply to the pituitary gland?
Pituitary arteries and the hypophysial portal circulation
What does the hypophysial portal circulation begin as?
A capillary plexus round the arc
What are the three layers of the endocrine system?
Primary- end organ
Secondary - pituitary
Tertiary - hypothalamus
What is the role of the hypothalamus?
Takes inputs from the brainstem and senses and higher centres and converts them into hormones that give a particular state
How does the hypothalamus work in conjunction with the pituitary gland?
Hypothalamus secretes small amount of hormone into hypophysial vein which runs into the pituitary which amplifies the hormone to the rest of the body
What are the clinical features of pituitary tumours?
Hormone hypersecretion, space occupying lesion, hormone deficiency states
What do the space occupying lesions cause?
Headaches, visual loss and cavernous sinus invasion
What does excess TSH lead to?
Secondary thyrotoxicosis
What does excess LH/FSH lead to?
Non functioning pituitary tumour
What does excess PRL lead to?
Prolactinoma
What is the function of GH on liver?
Stimulates liver to produce IGF-1 -> acts on chondrocytes in long bones to promote linear growth
What does acral enlargement involve?
Spade like hands, increased shoe size, macroglossia (big tongue), carpal tunnel syndrome
Give some external effects of GH excess (acromegaly)
Increased skin thickness, sweating, skin tags and increased interdental spacing
Give the systemic effects of acromegaly
Impaired fasting glucose and glucose tolerance, diabetes mellitus, insulin resistance, reduced cholesterol, increased TGs and nitrogen retention
What are the actions of cortisol?
Increases plasma glucose levels and lipolysis, protein catabolis, sodium and water retention, anti-inflammatory and increased gastric acid production
What processes increase when cortisol increases plasma glucose levels?
Gluconeogenesis, glycogenesis and glycogen storage
Why does cortisol increases lipolysis?
Conserve glucose by using broken down fats as energy
What are the external symptoms of Cushing’s syndrome?
Change in body shape, central obesity, moon face, thin skin and easy bruising
What does the change in sex hormones in cushings lead to?
Excess hair growth, irregular periods, problems conceiving and impotence (ED)
What does prolactin inhibit?
LH and FSH
What feedback mechanism controls prolactinomas?
Positive
What does tonic release of DA inhibit?
PRL release
What drugs interfere with DA and PRL secretion?
Antiemetics, antipsychotics and OCP/HRT
What is the name for the condition where a patient has PRL excess?
Hypogonadism
What are the symptoms of hypogonadism?
Infertility, amenorrhoea, reduced libido, oligoamenorrhoea, galactorrhoea and ED
What is amenorrhoea?
Complete stop of periods
What is galactorrhoea?
Milk release from breast
What is the treatment for hypogonadism?
Dopamine agonists like bromocriptine and cabergoline
What percentage of all pituitary tumours are non-functioning?
30%
What is the treatment for pituitary tumours?
Surgery
What is the optic chiasm?
Bit just above the pituitary where the signals from the two optic nerves meet
Why is the top of the field of vision lost first with a pituitary tumour?
Tumours will grow up from the bottom and the lens is inverted
What is the order of the loss of pituitary function with an expanding tumour?
LH and FSH -> GH -> TSH-> ACTH-> increased prolactin
What are the three treatments of pituitary adenomas?
Surgery, radiotherapy and drugs
What do the drugs do with pituitary adenomas?
Block hormone production or stop their release
What can cause pituitary failure?
Tumour, trauma, infection, inflammation or iatrogenic
What is iatrogenic?
Caused by medical treatment
What are the consequences of hypopituitarism on the thyroid?
Bradycardia, weight gain, cold intolerance, hypothermia, constipation
What are the consequences of hypopituitarism on the sex steroids?
Oligomenorrhoea, reduced libido, hot flushes and reduced body hair
What are the consequences of hypopituitarism on reduced cortisol?
Tiredness, weakness, anorexia, postural hypotension and myalgia
What is myalgia?
Muscle pain
When does excess ADH release happen?
In brain injury or infection where altered brain stimulus increases hypothalamic ADH production
What controls vasopressin release?
Increased plasma osmolality, decreased blood pressure
What is the action of ADH?
Increase the collecting ducts permeability for water and also vasoconstriction
What is the treatment for the syndrome of inappropriate ADH secretion?
Fluid restriction, demeclocycline and ADH antagonists
What causes diabetes insipidus?
Underproduction of ADH
What is the water deprivation test?
Body can tolerate 3% loss of body mass due to fluid loss - dont give them water for 8 hrs to see the changes in urine conc
What is a diabetic persons reaction to being given an ADH injection after the water deprivation test?
Plasma becomes concentrated - in cranial DI it goes back to normal but in nephrogenic DI, ADH conc stays the same
What is the difference between cranial and nephrogenic DI?
Cranial = lack of production and nephrogenic = receptor resistance
What is the treatment for DI?
ADH drugs
