Pitutary Disorders Flashcards
Clinical presentation of pituitary tumours
Mass effect of tumour on local structures - visual loss (due to upward growth of a pituitary tumor leading to pressure on the optic chiasm) headache (due to sideways growth of a pituitary tumor the pressure on the maxillary nerve and the Ophthalmic nerve)
Abnormality in pituitary function - can get hypo- or hyper-secretion
Deficiency of hormones
Small tumours usually cause Growth hormone deficiency - Short stature in children
Reduced quality of life in adults
As tumor increases in size it can lead to Gonadotrophin deficiency
Loss of secondary sexual characteristics in adults
Loss of periods an early sign in women
Again as tumor increases you can gain TSH and ACTH deficiency:
Late feature of pituitary tumours
TSH deficiency - low thyroid hormones, become cold, weight gain, tiredness, slow pulse, and low T4 and non elevated TSH
ACTH deficit - low cortisol, tired, dizzy, Low BP, low sodium - can be life threatening
Dynamic assessment of HPA and GH axes
Stimulation test - suspected hormone deficiency
Suppression test - suspected hormone excess
HP Adrenal axis
Deficiency - Direct stimulation of adrenals by ACTH (synACTHen)
- Response to hypoglycaemic stress (insulin stress test)
Excess - Suppress ACTH axis with steroids (dexamethasone)
GH axis -
Deficiency - Response to hypoglycamic stress (insulin stress test)
Excess - Suppress GH axis with glucose load (glucose tolerance test)
Could do a radiological assessment of pituitary disease - using MRI
Assessment of visual fields
Prolactinoma
Prolactin-secreting pituitary tumour
Large tumour = macro-adenoma (> 1cm) —>
Small tumour = micro-adenoma (< 1cm)
The larger the tumour, the higher the prolactin
Prolactinomas are treated with tablets not an operation
Even if the tumour is very large causing visual problems - never send a patient for surgery until prolactin is known
Macro-prolactinoma treatment - Tumour will shrink with dopamine agonist
Remember dopamine inhibits prolactin
Hyperprolactinaemia - Prolactin directly inhibits LH secretion
So too much Prolactin will inhibit LH’s affect on the ovaries/testis and will cause inhibition (due to negative feedback) on the hypothalamus to stop producing LH
Symptoms of hyperprolactinaemia in women
Menstrual disturbance, Fertility problems, Galactorrhoea, Milky discharge - In micro-prolactinomas serum prolactin is not that high
Symptoms of hyperprolactinaemia in men
Men present later than women (no periods)
Due to it being harder to detect - Usually larger tumours (macro-adenomas)
Symptoms of low testosterone are non-specific
May present with mass symptoms such as visual loss
Important point - high prolactin and pituitary mass, Prolactin is under tonic inhibitory control by dopamine
Anything blocking the infundibulum stalk will lead to prolactin disinhibition (no regulation on the amount of prolactin produced)
If prolactin < 5,000 the high prolactin might be due to disinhibition (‘stalk effect’) rather than active prolactin secretion
If prolactin > 5,000 the high prolactin is likely to be due to active prolactin secretion (prolactinoma)
This is important as prolactinomas are treated medically but non functioning pituitary tumours (No secretion of biologically active hormones, May secrete inactive hormones (e.g ACTH or LH / FSH) - inactive due to the hyperprolactinaemia, Clinical features are due to mass effect of symptoms from low pituitary hormones) are treated surgically
Treatment of prolactinoma - Dopamine agonists stimulate D2 receptor
Bromocriptine and cabergoline very effective at reducing prolactin
Remember dopamine antagonists can cause high prolactin Anti-sickness, anti-psychotic drugs
Always check medication in a patient with high prolactin level And make sure patient is not pregnant! I
Acromegaly
Large extremities’
Tell-tale sign is large hands and feet
GH-secreting pituitary tumour
Leading to gradual changes in features over years
Important for medical students to learn about this
The diagnosis is made by any doctor in any clinical setting
Long-term complications of untreated acromegaly
Premature cardiovascular death
Increased risk of colonic tumours
Probably increased risk of thyroid cancer
Disfiguring body changes that may be irreversible
Hypertension and diabetes
Unpleasant symptoms
Biochemical tests to confirm acromegaly
Oral Glucose Tolerance Test (OGTT) with GH response
Failure to suppress GH < 1 ug/L - if given a dose of inhibitor that would normally lower GH levels and it doesnt work - would indicate over secretion of GH
Elevated IGF-1 level (age related reference range)
Growth Hormone Day Curve (GHDC) – elevated mean GH
Treatment of acromegaly - Surgical removal of tumour
Trans-sphenoidal hypophysectomy
Very specialist surgery Safe in the right hands
Tumours in cavernous sinus need additional treatment
Additional treatment for acromegaly:
Medical treatment - 1) reduce GH secretion using drugs e.g.
Dopamine agonist - Cabergoline, Bromocriptine
Somatostatin analogues - Octretide, Lanreotide, Pasireotide
Both
2) block GH receptor - using the drug Pegvisomant - prevents GH binding to the liver, therefore no IGFs produced
3) Radiotherapy - External beam - Multiple short bursts over several weeks - called Gamma knife radiotherapy - High concentration over single time
Cushing’s disease
ACTH-secreting pituitary tumour
A very interesting condition
Classical change in appearance - Round pink face with round abdomen, Skinny and weak arms and legs, Thin skin and easy bruising, Red stretch marks (‘striae’) on abdomen, High blood pressure and diabetes and Osteoporosis (thin bones)
Caused by too much cortisol
Cushing disease vs Cushing syndrome
Cushing’s disease is 100% due to a pituitary tumour
Cushing’s syndrome may be caused by other pathologies
E.g. Adrenal tumour, ectopic ACTH, steroid medication
Diabetes Insipidus
Not to be confused with diabetes mellitus sugar diabetes (‘sweet’)
‘Diabetes’ is the Greek word for ‘Siphon’
Diabetes insipidus - Large quantities of pale (insipid) urine
Extreme thirst due to fluid loss
The posterior pituitary gland secretes vasopressin (ADH)
Anti-Diuretic Hormone
‘Diuresis’ means increased urine
‘Anti-diuresis’ means the opposite
In this disease, there is a lack of vasopressin being produced - hence the anti-diuretic effects it possess are not being “felt” by the body so fluid uptake is reduced - so you have a very dilute pale non sweet urine
Due to the lack of water retention in the blood, the concentration of glucose as a % is probably high, hence you have hyperglycaemia, leading to diabetes
