Lecture 16 Flashcards
What is the most common cause of pituitary malfunction?
Bengin tumour= Adenoma
How common are disorders of the pituitary gland?
Rare
What are the 2 types of pituitary tumours?
Non-functioning: Do not produce any hormone. Result in inadequate production of one or more pituitary hormones due to physical pressure on glandular tissue
Functional: Cause problems with overproduction of one or more of the pituitary hormones
How do pituitary tumours affect the patient clinically?
Non-functioning: headaches, visual problems (compression of optic nerve), vomiting, nausea
Functional: systemic effects of the over secreted hormone
How would you investigate/diagnose a suspected pituitary tumour?
- Locate the anatomy, size and location of mass- MRI scan
- Assess visual field defects
- Assess endocrine function by measuring levels of hormones in blood (excess/deficiency)
What is hypopituitarism and its causes?
Insufficient pituitary hormone production Causes: -pituitary adenoma -radiation therapy -inflammatory disease -head injury
In what order are the pituitary hormones lost?
GH and LH/FSH lost first, then TSH and ACTH, lastly PRL
ADH and oxytocin are only significantly affected if tumour affects hypothalamic function/inflammatory process is involved
What is panhypopituitarism?
Deficiency of all anterior pituitary hormones
What does GH deficiency in adults/children result in?
Adults
- decrease in tolerance to exercise
- decreased muscle strength
- increased body fat
- reduced sense of well-being
Children
- poor growth
- short stature
Why is GH deficiency hard to diagnose?
GH secretion is pulsatile
requires direct and indirect measurements
What are the causes of GH deficiency in children?
- idiopathic (unknown)
- gene mutations in GHRH receptor
- autoimmune inflammation
Does GH deficiency have any effect on fetal growth?
Little
-can result in hypoglycaemia/jaundice
How do you treat GH deficiency?
GH is manufactured by recombinant DNA technology
What does a gonadotropin deficiency cause?
- lack of libido (sexual desire)
- infertility
- infrequent periods (oligomenorrhea)
- no periods (amenorrhea)
- impotence (erectile dysfunction/failure to orgasm)
What causes a deficiency of ADH?
- hypothalamic tumour
- pituitary tumour that has extended up into the hypothalamus
- cranial radiotherapy
- pituitary surgery
- autimmune infiltration
- infections (meningitis)
What does insufficient ADH release lead to?
Excess excretion of dilute urine resulting in dehydration, and an increasedsensation of thirst (polydipsia)
=DIABETES INSIPIDUS
What are the 3 main conditions caused by excess pituitary hormone production due to hypersecreting pituitary adenoma?
- prolactin excess
- growth hormone excess
- ACTH excess
What does excess secretion of ACTH cause?
Cushing’s syndrome
What dominates the function/secretion of prolactin?
Inhibition of prolactin secretion by dopamine dominates
What is the most common form of pituitary disorder?
Hyperprolactinaemia (high prolactin level in blood)
What are the symptoms of hyperprolactinaemia?
- galactorrhoea (unexplained milk production-rare in men)
- gynecomastia (hard breast tissue)
- hypogonadism (diminshed activity of testes/ovaries)
- amenorrhea (no period)
- erectile dysfunction
Why does hypogonadism arise from hyperprolactinaemia?
- high levels of dopamine due to negative feedback from increased plasma prolactin
- high levels of dopamine inhibits GnRH/LH/FSH secretion from anterior pituitary
What is the most common cause of hyperprolactinaemia?
Prolactinoma- pituitary adenoma which secretes prolactin
-pregnancy, suckling, stress, exercise, drugs, antidepressants can also cause it
How do you treat prolactin excess?
- dopamine receptor agonists (cabergoline)
- trans-sphenoidal surgery (access pituitary through nose)
- radiotherapy
What do growth hormone secreting adenomas cause and how?
-headache
-visual field defects
-cranial nerve palsies
(they are usually large)
Direct actions of GH itself and via stimulation of IGF-1 production
How long does GH excess take to manifest?
Several years (can be up to 6 years)
What are some changes in physical appearance in GH excess?
- broad nose
- coarse facial features
- thick lips
- prominent supraorbital ridge (crest bone on frontal lobe of skull)
- enlargement of hands and feet
- skin is greasy with excessive sweating
- deepening of voice (hypertrophy of soft tissue in upper airways)
What is the condition where there is excessive GH secretion in children (before fusion of epiphyseal plates)?
Gigantism
rarely develops now due to early diagnosis and treatment
What does GH antagonise?
The actions of insulin
therefore diabetes mellitus may develop
What have the increase in IGF-1 levels in GH excess been associated with?
Some forms of cancer
What are the 3 treatment options for patients with acromegaly (too much GH in adults)?
- surgery to remove adenoma
- radiation therapy
- drug therapy
How can you reduce GH levels with drugs?
- Dopamine receptor agonists
- somatostatin which limits GH secretion has limited use due to short half life, but synthetic somatostatin analogs have been developed which produce prolonged suppression of GH secretion
- antagonists of GH receptor (pegvisomant) is the most recent treatment
In what nucleus of the hypothalamus is ADH made?
Supraoptic nucleus
In what nucleus of the hypothalamus is oxytocin made?
Paraventricular nucleus
What is pituitary apoplexy?
Sudden vascular event in a pituitary tumour
