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
What are CRH and ATCH? How are they involved in the release of cortisol?
CRH- corticotropin releasing hormone released by hypothalamus
Adrenocorticotropic hormone released by anterior pituitary
Stimulates release of cortisol from adrenal gland
What is hypopituitarism? How about pan-hypopituitarism?
Hypopituitarism= deficiency in one or more pituitary hormones Pan-hypopituitarism= deficiency in all pituitary hormones
What are some causes of hypopituitarism/pan-hypopituitarism?
Pituitary adenoma, radiotherapy of pituitary, damage to pituitary stalk due to head trauma
What can a deficiency in ADH lead to?
Diabetes insipidus (urinate lots and always thirsty, not related to diabetes mellitus)
What can a deficiency in gonadotropin lead to? What is the treatment for this?
Low LH and FSH= delayed puberty in children, infertility in adults
Treatment is hormone replacement therapy
Give two examples of dopamine receptor agonists. What are these used for?
Bromocriptine, cabergoline
Used to treat prolactinomas (inhibit release of prolactin and shrink tumour)
