Pituitary hormone regulation + presentation of pituitary disease Flashcards
What part of the pituitary glands has an arterial blood supply
The posterior pituitary glands
What thyroid controlled hormone is released by the hypothalamus
TRH
What does TRH stimulate in the pituitary glands
TSH
How does TSH effect the thyroid
Causes release of T4 and T3
Describe the pituitary gonadal axis
- GnRH secreted by hypothalamus
- GnRH down anterior pituitary via hypophyseal portal system
- GnRH stimulates anterior pituitary glands to secrete LH and FSH
- FSH and LH in females causes production of oestrogen and inhibin + regulates menstrual cycle
- LH in men causes testosterone production and FSH causes spermatogenesis
Describe the hypothalamic-pituitary-adrenal axis
- CRH and Vasopressin produced in nerve terminals of the medial eminence
- CRH moves down pituitary stalk and vasopressin is transported down axon to the posterior pituitary glands
- CRH and vasopressin stimulate secretion of stored ACTH.
- ACTH transported to adrenal gland
- Stimulates synthesis of corticosteroids such as cortisol and aldosterone
- Cortisol binds to miner corticoids receptors
Describe the negative feedback mechanism in the HPA axis
- Cortisol inhibits hypothalamus and pituitary glands - reduces levels of CRH and vasopressin
Describe the GH/IGF-I axis
- GnRH stimulates the pituitary
- Somatostatin inhibits pituitary
- Liver produces IGF-I
Role of IGF-I in GH/IGF-I axis
Inhibits hypothalamus
5 common diseases of the pituitary gland
- Benign pituitary adenoma
- Craniopharyngioma
- Trauma
- Apoplexy
- Sarcoid
What is pituitary apoplexy
Bleeding into or impaired blood supply of the pituitary gland - tumours
Why does pituitary glands cause bitemporal hemianopsia
Temporal vision crosses over at the optic chasm. Pituitary gland tumours can compress the optic chiasm leading to temporal vision being lost.
What are the three important presentations of a pituitary disease
- Pressure one local structures
- Pressure on normal pituitary function (hypo/hyperpituitarism)
- How tumour is affecting levels in the body of other hormones (prolactinoma, Acromegaly and Cushing’s disease)
Why would a pituitary tumour cause headaches
Pituitary gland can place pressure on the dura mater
Pituitary gland could lead to hydrocephaly
How would lateral extension of a pituitary gland effect an individual
Cranial nerves will be squished
Temporal lobe epilepsy
What is an epilepsy
Sensory disturbances in the brain
How would downward extension of the pituitary tumour effect an individual
Lead to cerebrospinal fluid rhinorrhoea (breaks through CSF space)
What is cerebrospinal fluid rhinorrhoea
Drainage of CSF through the nose
What is a microadneoma
A tumour less than 10mm in diameter
Symptoms of prolactinoma
Hyperprolactinemia Vision problems (as gland causes bitemporal hemaniopsa) Loss of libido Galactorrhea Amenorrhea
How does an excess of prolactinoma effect males
Erectile dysfunction
What is a macro adenoma
Greater than 10mm diameter
In what sex is prolactinoma more common
Women
How is prolactinoma treated
Dopamine agonist (Cabergoline and Bromocriptine)
How is Cushing’s syndrome caused
Excess of cortisol
Pathophysiology of cushion’s syndrome
- Adenoma of pituitary gland causes excess production of ACTH in response to excess CRH
- ACTH levels stay high as tumour is unresponsive to negative feedback
- ACTH causes excess cortisol to be produced
How does excess cortisol cause the symptoms associated with cushing’s syndrome
- Central obesity (in the stomach not in legs and arms)
- Osteoporosis
- Muscle and bone weakness
- Diabetes
- Hypertension
- Hyperpigmentation
- CVD
In summary, what three questions do we ask a patient we suspect has a pituitary tumour
- Is it pressing the optic chimes
- Are they hypopituitary
- Do they have a functioning tumour
