2. Hypersecretion of Anterior Pituitary Hormones Flashcards
Hyperpituitarism definition
Symptoms associated with excess production of adenohypophysial hormones
This usually manifests due to isolated pituitary tumours
- It can also be ectopic in origin e.g vasopressin producing lung tumours
- Associated with visual field defects
- Also associated with other defects, brough about by compression of the cranial nerve
Bitemporal (heteronymous) hemianopia
Many people with pituitary tumours are picked up by their optician due to visual field defects:
- At the optic chiasm the fibres from the nasal part of the retina cross over
- A pituitary tumour could protrude out of the sella turcica and disrupt the fibres coming from the nasal parts of the retinae
- This means that you loose the temporal part of your field of vision
Diseases of Hyperpituitarism
Hyperprolactinaemia definition
Excess circulating prolactin when not due to a physiological cause such as pregnancy or breast feeding
associated with prolactinomas
- High levels of prolactin has an effect on the reproductive axis
- It decreases LH and FSH levels leading to secondary amenorrhoea
- Galactorrhoea (milk production) in men is very uncommon but it can happen
- Low LH and FSH levels also causes loss of libido, impotence and infertility
Acromegaly
- INSIDIOUS onset
- Signs and symptoms progress very gradually over many years
- If untreated both this and giantism can cause increased morbidity an mortality due to CVS and respiratry disease
- Increased organ size as well as increased bone growth
- Therefore increased dmeand for oxygen and CV stress
Tissue growth associated with acromegaly
- Periosteal bone
- Cartilage
- Fibrous tissue
- Connective tissue
- Internal organs (cardiomegaly, splenomegaly, hepatomegaly etc.)
- Prognathism
- Enlarged supraorbital ridges
- Enlarged soft tissues
Excess somatotrophin effect in children and adults
in CHILDREN= GIANTISM
in ADULTS= ACROMEGALY
Other common clinical signs of acromegaly
- Enlargement of supraorbital ridges
- Englargement of nose, hands and feet
- Thickening of lips
- Hyperhydrosis
- Mandible grows leading to protrusion of the lower jaw (prognathism)
- Carpel Tunnel Syndrome- due to increased cartaligenous growth leading to increasing pressure on the nerves
- Barrel chest/ kyphosis
- Galactorrhoea (often in women and occasionally in men) - at very high levels, GH has some prolactin like effects
- Abnormal glucose tolerence- symptoms of diabetes mellitus
Diagnosis and treatment of pituitary hypersecretory states
With HYPO you must do a stimulation/ provacation test.
With HYPER you do a SUPPRESSION TEST
glucose indiced suppression of growth hormone secretion
- insulin induced hypoglycaemia is used to stimulate GH release
- So Instead you give glucose to inhibit hormone release
- Giving glucose to someone with acromegaly infact gives the OPPOSITE EFFECT- there is a paradoxical rise in GH
Treatment of Acromegaly
Surgery is the main treatment- transphenoidal hypophysectomy
Radiotherapy- may end up having hypopituitary disease
Chemotherapy via:
- Somatostatin analogues e.g octreotide
- Dopamine agonists e.g bromocriptine
Clinical uses of ocreotide
- Short term treatment before pituitary surgery (can also reduce size of tumour)
- long term treatment in those not controlled by other means
- Treatment of other neoendocrine tumours
Unwanted side-effects of octreotide
- GI tract disturbances (somatostatin is produced by the small intestine)
- Initial reduction in insulin secretion - transient hyperglycaemia
- Octreotide inhibits the production of insulin by beta cells leading to transient hyperglycaemia
- Rarely gallstones
Treatment of Hyperprolactinaemia
Dopamine receptor agonists
REMEMBER: Dopamine is the main hypothalamic influence on prolactin secretion - it inhibits prolactin secretion
DA2 agonists DECREASES prolactin (and GH) secretion and REDUCES the tumour size
E.g Bromocriptine, Cabergoline
Bromocriptine
- DA2 antagonist
- Administered by mouth, mostly plasma bound
- half life= 7 hours
- Unwanted effects:
- Nausea/vomiting/abdominal cramps, Dyskinesias, Psychomotor excitation, Postural hypotension, Vasospasm in fingers and toes (caution Raynaud’s disease)
- Other uses:
- Suppression of lactation, in acromegaly to reduce tumour size, Parkinson’s disease
