Pituitary Disorders Flashcards
What is the mass efffect of pituitary tumour local structures?
Optic chiasm (vision)
III, IV nerve effected (eye movement)
Va,b nerve effected (pain)
What are the clinical presentation of pituitary tumours?
Not cancer - benign so will not die.
Mass effect of tumour on local strctures - visual loss (tunnel vision) due to pressue in optic chiasm or double vision and headches (stretching of local structures).
Abnormality in pituitary function as a result of hypo or hyper secretion of pituitary hormones.
What hypothalamus hormones control the anterior pituitary?
Positive control
- GH +
- LH / FSH +
- TSH +
- ACTH +
Negative control
- Prolactin -
The hypothalamus inhibits prolactin but stimulates everything else.
If a mass is blocking the stalk then all hormones under positive control will do down but prolactin will go up.
What are the consequences of growth hormone deficiency?
- Symptoms of GH deficiency in adults are quite subtle. Patients may show a decrease in tolerance to exercise, decreased muscle strength, increased body fat and a reduced sense of “well-being”.
- GH secretion is pulsatile so deficiency is often difficult to diagnose and a combination of direct and indirect measurements are required.
- GH deficiency in adults is usually due to the mass effects from a pituitary adenoma.
- Growth hormone deficiency in children is typically idiopathic (of unknown cause) but specific gene mutations (e.g. in the Growth- hormone-releasing hormone receptor) and autoimmune inflammation have been identified in some cases.
- GH deficiency has little effect on fetal growth. However, severe prenatal deficiency can result in hypoglycaemia and jaundice.
- From around 1 year of age until mid- teens GH deficiency results in poor growth and short stature. Human GH manufactured by recombinant DNA technology can be used as treatment for such cases.
What are the consequences of gonadotropin deficiency?
- Delayed puberty in children.
- Loss of secondary sexual characteristics in adults.
- Gonadotropin deficiency (hypogonadism) due to mass effects from a pituitary adenoma.
- It can result in lack of libido, infertility and oligomenorrhea or amenorrhea in women of reproductive age.
- Hypogonadism in men can also decrease libido and cause impotence.
What are the consequences of TSH and ACTH deficiency?
Late featuresof pituitary tumours.
TSH deficiency - low thyroid hormones, cold, weight gain, tiredness, slow pulse. low T4 and non-elevated TSH.
ACTH deficiency - low cortisoll, tired, dizzy, low BP, low sodium, HPA axis most important. This can be life threatening.
What hormones can be produced in excess?
- This excess is caused by a microtumour
- Prolactin - causes milk to be produced out of breasts
- GH
- ACTH
- TSH and LH/FSH excess is rare.
How do you biochemically assess pituitary disease?
Thyroid axis: fT4, TSH
Gonadal axis: LH, FSH, testosterone - men, oestradiol - women.
Prolactin axis: serum prolactin.
HPA axis: 09:00 cortisol (if deficiency - if looking for excess then measure at midnight)
GH axis: GH / IGF-1
Dynamic assessment of HPA and GH axes?
Stimulation test: suspected hormone deficiency
Suppression test: suspected hormone excess
Adrenal axis
Deficiency: Direct stimulation of adrenals by ACTH (synACTHen), response to hypoglycaemic stress (insulin stress test)
Excess: Suppress ACTH axis with steroids
GH axis
Deficiency: Response to hypoglycamic stress (insulin stress test)
Excess: Suppress GH axis with glucose load (glucose tolerance test)
Radiological assessment of pituitary disease
MRI
What is a Bitemporal hemi-anopia?
This is when you can’t see in certain fields of vision. It is indicative of pituitary tumous.
What is a prolactinoma?
This is a prolactin-secreting tumour. It is the most common cause of high prolactin.
The larger the tumour, the higher the prolactin.
Prolactinomas are treated with tablets of dopamine agonist (such as cabergoline) and not an operation - even if the tumour is very large and causing visual problems.
In rare cases however, trans-sphenoidal surgery (a type of surgery used to access the pituitary gland through the nose and sphenoid bone of the skull) or radiotherapy may be required.
Other than prolactinoma, what other things can cause excess prolactin?
The most common cause of hyperprolactinaemia is prolactinoma, a pituitary adenoma that secretes prolactin.
However, physiological causes such as pregnancy, suckling, stress and exercise and drugs such as antipsychotics (e.g. haloperidol) and antidepressants (e.g. clomipramine) can also cause hyperprolactinaemia.
What are the symptoms of hyperprolactinaemia?
Women:
- Menstrual disturbance e.g. amenhorrea
- Fertility problems
- Galactorroea (unexplained milk production (rare in men))
- Gynecomastia (hard breast tissue)
- Hypogonadism (diminished activity of testes or ovaries)
Men:
- Men often present later than women as no periods
- Usually larger tumours (macroadenomas)
- Symptoms of low testosterome are non specific
- May present with mass symptoms such as visual loss
- Erectile dysfunction.
- Hypogonadism (diminished activity of testes or ovaries)
Why are prolactinomas treated with dopamine agonists such as cabergoline or bromocriptine?
Prolactin secretion from the anterior pituitary is mainly under the negative influence of dopamine (referred to as prolactin inhibiting hormone in many texts) released from the hypothalamus.
Therefore, agonists stimulate the D2 receptor and cause dopamine to be produced which inhinits prolactin secretion.
