Normal Pituitary Function Flashcards
What is the most common cause of pituitary disease?
Pituitary tumours (adenomas)
What are the main signs/symptoms of a pituitary tumour?
Over-production of pituitary hormones, inadequate production of other hormones, impact on near-by structures (e.g. impaired vision)
Describe the nature of most pituitary tumours
Usually adenomas, benign, slow-growing (years)
When is the stimulation test used? Give an example. What happens in a test with a normal vs. abnormal result?
. When hyposecretion is suspected (e.g. secondary hypothyroidism)
. Normal: Inject TRH –> stimulates increased release of TSH by ant pit., thus increase T3/T4 produced by thyroid gland
. Abnormal: Inject TRH –> little/no effect on ant pit., doesn’t secrete much TSH
. Thyroid only releases small bit of T3/T4
When is the suppression test used? What happens in a normal test and in a positive test?
. When hypersecretion is suspected (e.g. acromegaly, tumour secreting GH)
. Raise blood glucose (oral tablet)
- Normal: increase GHIH, decrease somatostatin= suppress release of GH
- Abnormal: Secretion of GH by ant. pit not regulated by hypothalamus (GHIH, somatostatin) –> Failure to suppress indicates autonomous secretion
How is thyroid hormone secretion regulated?
Hypothalamus releases TRH, anterior pituitary releases TSH (thyrotropin), thyroid gland secretes T3/T4
Identify the location of the pituitary gland, hypothalamus, Sella turcica, and optic nerve in an MRI scan
(Check lecture slide examples/Google)
What is the preferred treatment for pituitary tumours? Give two ways in which this can be carried out and two side effects.
. Surgery
. Craniotomy (through skull above eye) or trans-sphenoidal (through nose)
. Risk of hypopituitarism and damage to optic pathways
What is the most common cause of hyperprolactinaemia? What are the symptoms of this?
. A prolactinoma can cause hyperprolactinaemia (secretes excess prolactin)
. Loss of fertility, libido, galactorrhoea (nipple discharge) gynaecomastia
How does the hypothalamus restrain the anterior pituitary from releasing prolactin?
Hypothalamus releases dopamine, which inhibits release of prolactin
What is the usual treatment for a prolactinoma? What if this doesn’t work?
Dopamine receptor agonists (e.g. bromocriptine, cabergoline)
Increase dopamine release= decrease prolactin release, and also shrinks tumour
If resistant to drug treatment, do surgery or radiotherapy
What is acromegaly? What is the most likely cause?
Release of excessive growth hormone in adults (GH stimulates liver to produce IGF-1)
(in children this is called ‘gigantism’)
Most common cause is GH-secreting tumour
Give some symptoms of acromegaly
Enlarged hands and feet, headaches, vision problems, tiredness, hypertension, diabetes, impotence (males), irregular or absence of periods (in women), gaps between teeth (as jaw enlarges)
What is the treatment for gigantism?
Surgery/radiotherapy to remove tumour
Somatostatin analogues to inhibit release of GH
What is Cushing’s syndrome? How is it treated?
Excessive glucocorticoid activity, can be endogenous (ACTH-secreting tumour in ant. pit.) or exogenous (caused by medication)
Treated by removing tumour/radiotherapy
