Hypersecretion of anterior pituitary hormones Flashcards
What is hyperpituitarism?
Excess production of adenohypophysial hormones.
What is hyperpituitarism usually caused by?
Isolated pituitary tumours
Can also be ectopic (i.e. from non-endocrine tissue), e.g. vasopressin-producing lung tumours
What defects is hyperpituitarism commonly associated with?
Visual field defects
Cranial nerve defects- effects on nearby structures to the pituitary
How may hyperpituitarism result in loss of temporal vision?
At the optic chiasm, fibres from the nasal retinae cross. Light from the temporal aspect of the visual fields strikes the nasal aspect of the retina. Compression of these fibres e.g. by a pituitary tumour protruding out of the sella turcica may result in bitemporal (heteronymous) hemianopia.
What does excess ACTH (corticotrophin) result in?
Cushing’s disease
What does excess TSH (thyrotrophin) result in?
Thyrotoxicosis
What does excess FSH/LH (gonadotrophins) result in?
Precocious puberty in children
What does excess prolactin result in?
Hyperprolactinaemia
What does excess GH result in?
Gigantism (children); acromegaly (adults)
What is hyperprolactinaemia?
Excess circulating prolactin due to physiological (pregnancy or breastfeeding) or pathological (prolactinoma- microadenoma) causes.
What can hyperprolactinaemia due to prolactinoma result in in women?
Galactorrhoea
Secondary amenorrhoea (low LH and FSH)
Loss of libido
Infertility
What can hyperprolactinaemia due to prolactinoma result in in men?
Loss of libido
Impotence
Infertility
Galactorrhoea uncommon (appropriate steroid background usually inadequate)
What is the first-line treatment for hyperprolactinaemia?
Dopamine receptor (D2) agonists, e.g. bromocriptine, cabergoline- decrease prolactin secretion and reduce tumour size. Oral administration.
Name some side effects of dopamine receptor (D2) agonists used to treat hyperprolactinaemia.
Nausea and vomiting Postural hypotension Dyskinesias Depression Pathological gambling
What is acromegaly?
Excess somatotrophin (GH) in adults. The growth plates of the long bones have fused so there is no longer a possibility of an increase in height- still get other effects. It has insidious onset- signs and symptoms progress gradually over many years.
What happens if acromegaly/gigantism is left untreated?
Associated with increased morbidity and mortality due to cardiovascular (majority) and respiratory complications. It is not just increased growth but also increased organ size. This means there is increased demand for oxygen and the blood supply must keep up with this extra demand- big strain on CVS.
What symptoms are associated with acromegaly?
Increased growth of periosteal bone, cartilage, fibrous tissue, connective tissue, internal organs (cardiomegaly, hepatomegaly, splenomegaly, etc.) Prognathism Enlarged supraorbital ridges and soft tissues Excessive sweating (hyperhidrosis) Headaches Macroglossia Carpal tunnel syndrome Barrel chest Kyphosis
What are the metabolic effects of acromegaly?
Excess GH causes increased endogenous glucose production and decreased muscle glucose uptake. This leads to increased insulin production and thus increased insulin resistance. There is then impaired glucose tolerance (50% patients) and subsequent diabetes mellitus (10% patients).
Name some complications of acromegaly.
Obstructive sleep apnoea- bone and soft tissue changes surrounding the upper airway lead to narrowing and subsequent collapse during sleep.
Hypertension- direct effects of GH and/or IGF-1 on vascular tree; GH-mediated renal sodium reabsorption.
Cardiomyopathy- hypertension, DM, direct toxic effects of excess GH on myocardium.
Cancer- colonic polyps, regular screening with colonoscopy.
How are pituitary hypersecretory states diagnosed?
Suppression tests
How is acromegaly diagnosed?
Glucose-induced suppression of growth hormone secretion (oral glucose tolerance test).
Glucose should inhibit GH release so GH levels will decrease, with an over-swing at the end.
In a patient with acromegaly, there is a paradoxical rise in GH following administration of glucose.
Elevated serum IGF-1.
How is acromegaly treated?
Surgery (trans-sphenoidal) is first-line.
Medical treatments include somatostatin analogues, e.g. octreotide, and dopamine agonists (GH secreting pituitary tumours frequently express D2 receptors), e.g. cabergoline.
Radiotherapy may also be used.
What are somatostatin analogues used for?
‘Endocrine cyanide’, subcutaneous injection (short acting) or monthly depot.
Reduce GH secretion and tumour size.
Pre-treatment before surgery may make resection easier.
Use post-operatively if not cured or whilst waiting for radiotherapy to take effect (slow).
GI side effects are common, e.g. nausea, diarrhoea, gallstones can occur.
