Pituitary hormone regulation Flashcards
What is the posterior pituitary made up of and what 2 hormones are released?
It is made of the paracentricular and supraoptic nucleus
- It releases oxytocin and ADH
What is the anterior pituitary made up of and what hormones are released from the anterior pituitary?
Made up of glandular tissue
TSH released as a response to TRH
ACTH released as a response to CRH
FSH & LH released as a response to GRH
GH released as a response to Somatostatin
Prolactin as a response to lactotrophs (constantly inhibited by dopamine secretion)
What is the portal circulation of the pituitary?
Anterior pituitary has no arterial supply, it receives its blood supply from the portal venous circulation from the hypothalamus.
Describe the pituitary-thyroid axis
- Hypothalamus produces TRH
- Pituitary releases TSH
- Thyroid gland produces T3 and T4
- These negatively feedback to the hypothalamus & pituitary to stop releasing TRH
Describe the pituitary-gonadal axis
- Hypothalamus releases GnRH
- Pituitary releases LH and FSH
- In men LH stimulates testosterone production
- In men FSH stimulates spermatogenesis
- Testosterone negatively feedbacks to the hypothalamus & pituitary
- In women LH stimulates estradiol
- In women FSH important in ovulation
- Estradiol and progesterone feedback again
Describe the hypothalmic-pituitary adrenal axis
- Hypothalamus releases CRH
- Anterior pituitary releases ACTH
- Adrenal cortex releases cortisol
- Cortisol neg feedbacks to pituitary and hypothalamus to stop producing hormone
Describe the growth hormone axis
- Hypothalamus produces GHRH (increases secretion) & somatostatin (decreases secretion)
- Pituitary releases GH in pulsatile manner
- Liver produces IGF-1 that negatively feedback to hypothalamus
- Ghrelin also stimulates release of GH from pituitary
Describe the Prolactin Axis
- Prolactin is constantly under negative control by the hypothalamus by dopamine
- If pituitary stalk is damaged and dopamine is not produced, prolactin will not be inhibited and prolactin increases
Causes of pituitary disease? (5)
- Benign pituitary adenoma = most common (can inflame and cause pressure on other organs)
- Craniopharyngioma - benign tumour between hypothalamus and anterior pituitary (more common in children, can press on nearby organs)
- Trauma - car accident can cause severe head damage or can section the pituitary stalk and lead to hypopituitarism
- Apoplexy/Sheehans syndrome - pituitary tumour which bleeds and can swell and block off blood supply (rare) - hypopituitarism
- Sarcoid/TB - rare which can cause inflammation of pituitary
What 3 vital things can pituitary tumours cause?
- Pressure on local structures - optic nerve (bitemporal hemianopia)
- Pressure on normal pituitary - hypopituitarism
- Functioning tumour - prolactinoma, acromegaly, cushing’s disease
Describe what occurs when a pituitary tumour causes pressure on local structures depending on the direction of growth
- Pressure upwards = can get headaches
- Pressure backwards = hydrocephalus (rare)
- Pressure on optic chiasm = pressing on crossing over bit of optic chiasm = bitemporal hemianopia
- Pressure sideways = cranial nerve palsies and temporal lobe epilepsy
- Third nerve palsy = eye goes down and out & ptosis (drooping) and pupilary dilation
- Pressure downwards = cerebrospinal fluid rhiorrhoea
- Tumour can erode down through the sella tursica and through the sphenoid sinus and we can get CSF leak from the nose
What are the symptoms of hypopituitarism?
Pale
No body hair
Central obesity
What are the 3 functioning pituitary tumours?
- Prolactin microadenomas
- Acromegaly and gigantism
- Cushings disease
How might someone with prolactin microadenoma present?
What is the treatment for them?
- more common in women
- loss of libido
- visual field defect
- amenorrhea, irregular periods, infertility and galactorrhoea
Treat with dopamine agonist = cabergoline or bromocriptine
What is the difference between acromegaly and gigantism? What are the signs?
Acromegaly = occurs when excess GH produced after the epiphyseal plates have fused.
- Enlarged features such as jaw, hands, feet, lips, thick skin.
Gigantism = occurs when the epiphyseal plates have not fused so long bones can grow and child becomes very tall
