Pituitary Flashcards
What is the most common cause of a pituitary malfunction?
Benign tumour (Adenoma)
How can a ‘non-functioning’ tumour result in inadequate production of one or more pituitary hormones?
Due to the physical pressure form the growing tumour on the glandular tissue.
What issues can a pituitary tumour cause when you think about the pressure it applies to surrounding structures?
Headaches and visual problems (compression of the optic nerve), vomiting and nausea
What are effects of a ‘functional’ pituitary tumour?
If depends, they correspond to the systemic effects of the over secreted hormone.
There may not be any negative feedback regulation of the hormone.
What 3 things are involved with investigation a suspected pituitary tumour?
- Delineation of anatomy, size and topographical location of the pituitary or parapituitary mass (usually by MRI scan)
- Assessment of visual field defects
- Assessment of endocrine function to determine whether there is hormonal excess or deficiency.
How would you Assess the endocrine function to determine whether there is hormonal excess or deficiency?
- Measuring the hormone levels in blood
2. staining sections from a biopsy of the tumour with antibodies for the relevant hormone
What is hypopituitarism?
Insufficient pituitary hormone production
What are the causes of hypopituitarism?
- Pituitary adenoma
- Radiation therapy
- Inflammatory disease
- Head injury
What are the first hormones secreted by the anterior pituitary to be lost due to a pituitary adenoma?
GH and LH/FSH
What is a deficiency in all anterior pituitary hormones referred to as?
Panhypopituitarism
When might the secretion of ADH and oxytocin from the posterior pituitary be affected?
If a tumour is affecting the hypothalamic function
Or
If an inflammatory process in involved
What effects would a growth hormone deficiency have on an adult?
Decreased exercise tolerance
Decreased muscle strength
Increased body fat
Reduced sense of ‘well being’
Why is a GH deficiency so difficult to diagnose?
Because the secretion of it is pulsatile
What effect does GH deficiency have on foetal growth?
Little effect
*sever prenatal deficiency can result in hypoglycaemia and jaundice
What are the results of a gonadotropin deficiency? *called hypogonadism
Women: Lack of libido,
Infertility
Oligomenorrhoea (irregular periods) or amenorrhea
Men: decrease libido and impotence
What are the causes of a ADH deficiency?
hypothalamic tumour
pituitary tumour that has extended up into the hypothalamus.
Other causes of ADH deficiency include cranial radiotherapy, pituitary surgery autoimmune infiltration and infections such as meningitis
What are the consequences of ADH deficiency?
Excess excretion of dilute urine=dehydration and increased sensation of thirst (polydipsia)
*this condition represents the cranial form of the disease diabetes insipidus
What are the three main conditions caused by excess pituitary hormone production from a hyersecreting pituitary adenoma?
Prolactin excess
Growth hormone excess
ACTH excess
What secretes prolactin?
Lactotropes in the anterior pituitary
*stimulated by prolactin releasing hormone, inhibited by dopamine (more important control)
What can hyperprolactinaemia cause, symptom wise?
- Galactorrhea (unexplained milk production-rarer in men)
- gynecomastia (hard breast tissue)
- Hypogonadism
- Amenorrhea
- Erectile dysfunction
What are the causes of hyperprolactinaemia?
Common: prolactinoma (pituitary adenoma that secretes prolactin)
Other causes: pregnancy, suckling, stress and exercise, drugs (antipsychotics and antidepressants)
How is hyperporlactinaemia treated?
Using dopamine receptor agonists (ie cabergoline)
These stimulate dopamine secretion which in turn will inhibit prolactin secretion
If using dopamine receptor agonists doesnt help someone with hyperprolactinaemia, what other treatments are there?
Trans-sphenoidal surgery)
Radiotherapy
Why do growth hormone excess take so long to diagnose?
Because the effects of it will often take several years to manifest as a change in physical appearance
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