Pituitary Flashcards
Where is the pituitary gland?
Between and behind eyes
Deep in the brain
Like two grapes hanging off the hypothalamus
Describe the structure of the pituitary?
Attached to hypothalamus via the infundibulum (stalk)
Two ‘lobes’ anterior and posterior
What is a hypophysis?
Another name for pituitary gland
Blood supply of pituitary?
Posterior pituitary receieves blood from many arteries
Anterior pituitary receives blood from a portal vein from the hypothalamus
What is the name of the portal venous system that supplies the anterior pituitary?
Hypothalamo-hypophysial portal system
What does the pituitary do?
Produces different hormones which regulate the function of all the endocrine glands
List some effects that hormones made by the pituitary have on the body?
Growth
Thyroid function
Puberty
Steroid production in body
What control pituitary function?
Hypothalamus
How does the hypothalamus communicate with the anterior pituitary gland?
Hypothalamus secretes a hormone into the hypothalamo-hypophysial portal system
It goes to the anterior pituitary, stimulating the pituitary to release hormones
Which hormones are produced in the anterior pituitary? What are the target organs for these hormones?
Growth hormone: bones + soft tissues
Adrenocorticotropic hormone (ACTH): adrenals
Thyroid stimulating hormone: thyroid
FSH and LH: ovaries and testes
Prolactin: breast
Which hormones does the posterior pituitary gland make?
What are the target organs for these hormones?
Anti-diuretic hormone: kidney
Oxytocin: breast, uterus in labour
How does the hypothalamus communicate with the posterior pituitary gland?
Neuronal communication
Name some diseases of the pituitary?
Benign adenoma Craniopharyngioma Trauma Apoplexy / Sheehan's Sarcoid / TB
What problems does benign adenoma of pituitary cause?
Pressure on local structures: optic chiasm, dura
Raised ICP
Pituitary hormone production problems (deficiency or excess)
What is a craniopharyngioma?
Childhood tumour affecting the hypothalamus and pituitary
Clinical features of craniopharyngioma?
Raised ICP
Visual problems
Pituitary hormone deficiency
What visual problems occur when a pituitary tumour presses on the optic chiasm?
Bilateral hemianopia
What happens when a pituitary tumour presses on the dura?
Headaches
What happens when a pituitary tumour causes deficiency of pituitary hormones?
Hypopituitarism
Clinical features of hypopituitarism?
Pale
Central obesity
Lack of body hair
Amenorrhoea in women
What are functioning pituitary tumours?
Tumours of pituitary that cause it to release excess of the normal hormones it produces
Name the big 3 conditions caused by functioning pituitary tumour?
Prolactinomas
Acromegaly
Cushing’s syndrome
Difference between microadenoma and macroadenoma?
Micro = less than 1cm Macro = more than 1cm
You suspect a patient has a problem with the hypothalamus-pituitary-thyroid axis.
How do you investigate?
Measures levels of
TSH
T3 and T4
What levels of TSH, T3 and T4 would you expect to see in primary hypothyroidism?
Low T3, T4
High TSH
Thyroid is not working so low T3 and T4
Pituitary tries to compensate so releases more TSH
What levels of TSH, T3 and T4 would you expect to see in hypopituitarism?
Low T3, T4
Low TSH
Pituitary is not producing enough TSH
So it is not stimulating thyroid to make T3 and T4
What levels of TSH, T3 and T4 would you expect to see in Grave’s disease?
High T3, T4
Low TSH
Thyroid is overactive so too much T3 and T4 produced
Pituitary senses high levels so releases less TSH to try to compensate
What is a TSHoma?
A tumour of the pituitary that releases too much TSH
What levels of TSH, T3 and T4 would you expect to see in THSoma?
High T3, T4
High TSH
Tumour causes excess TSH
Which stimulates more T3 and T4 production
You suspect a patient has a problem with HIS hypothalamus-pituitary-gonadal axis.
How do you investigate?
Measure levels of
Testosterone (T)
FSH and LH
What levels of T, FSH and LH would you expect to see in primary hypogonadism?
Low T
High FSH and LH
Problem with gonads (testes) so reduced production of T
Pituitary tries to compensate by producing more FSH and LH
What levels of T, FSH and LH would you expect to see in hypopituitary?
Low T
Low FSH and LH
Pituitary is not releasing enough FSH and LH
So gonads are not being stimulated to make T
What levels of T, FSH and LH would you expect to see in excessive anabolic steroid use?
Low T
Low FSH and LH
Anabolic steroids disrupt this pathway
You suspect a patient has a problem with HER hypothalamus-pituitary-gonadal axis.
How do you investigate?
Measure levels of
Oestradiol (O)
FSH and LH
What levels of O, FSH and LH would you expect to see in primary ovarian failure?
Low O
High FSH and LH
Dysfunctioning of ovary means no O production
Pituitary tries to compensate so more FSH and LH
You suspect a patient has a problem with their hypothalamus-pituitary-adrenal axis.
How do you investigate?
Measure cortisol levels
Synacthen test: give them a synthetic version of ACTH
If healthy, cortisol levels should rise as the ACTH is triggering the adrenals to make cortisol
What result would you see when doing a synacthen test on someone with primary adrenal deficiency?
Poor
problem is in adrenals, no amount of extra ACTH makes the adrenals work better to make more cortisol
What result would you see when doing a synacthen test on someone with hypopituitarism?
Increase in cortisol level, because the person is deficient in ACTH.
If you replace the ACTH the adrenals will be stimulated to produce cortisol
What does ACTH stand for?
AdrenoCortioTropic hormone
What controls prolactin secretion?
Dopamine!
Not the hypothalamus
How would you investigate problems with prolactin axis?
Measure prolactin levels:
Prolactin is a stress hormone, more is released in times of stress
Cannulate the patient (cause stress) and then measure prolactin levels for an hour after.
You should see prolactin levels fall
