L16: Pituitary disorders Flashcards
What are pituitary disorder?
Over- or under-secretion of pituitary hormones
Most common causes is a benign tumour (adenoma)
What are non functioning tumours?
Tumour cells do not produce any hormone
Inadequate production of one or more hormones
Due to compression of tumour on glandular tissue
Lateral growth/ compression–> pain and double vision
Superior growth/ compression –> Bitemporal hemi-anopia (tunnel vision)–> lateral field of view lost
(light travels in straight lines so lateral field will be picked up on middle part of retina which is lost??)
What are functional tumours?
Usually hypersecreting
Over production of hormone
How are pituitary tumours investigated and diagnosed?
- MRI scan–> delineation of the anatomy, size and topographical location of the pituitary or parapituitary mass
- Assessment of visual field defects
- Assessment of endocrine function–> hormonal excess or deficiency–> measurement of hormone levels in blood, or by staining sections from a biopsy with antibody for relevant hormone
How can biochemical assessment be useful for determining pituitary disease?
Basal blood test sufficient for somethings
- Thyroid axis –> fT4, TSH
- Gonadal axis–> LH, FSH
- Prolactin axis–> serum prolactin
Dynamic blood test needed for some
- HPA axis –> cortisol–> circadian rhythm control
- GH axis–> GH/ IGF-1
–> Not enough hormone–> stimulate it see what happen
–> Too much –> supress it see if the level decrease–> if not sign of a tumour
How does the dynamic assessment of adrenal axis work?
Suspect deficiency
–> inject synACTHase–> monitor cortisol level T=0 and T=30–> increase shows adrenal glands functioning
OR
–> Insulin stress test–> stress the body (hypoglycaemic stress)–> See if ACTH and cortisol levels increase–> if so pituitary glands working
Suspect excess
–> Inject steroids (dexamethasone)–> see if cortisol levels decrease–> if they don’t autominal cortisol secretion
How does the dynamic assessment of growth hormone axis work?
Suspect deficiency
–> Insulin stress test–> Hypoglycamic stress–> GH should increase to couteract insulin
Suspect excess
–> Glucose tolerance test–> give glucose–> GH should fall–> if not autominal secretion
What is hypopituitarism? Which hormones are decreased and which are increased? Why?
Insufficient hormone production
Deficiency in all –> panhypopituitarism
Common result of pituitary adenoma–> prevents hormone release
Reduced–> GH (GHRH), LH/FSH (GnRH), TSH (TRH) and ACTH (CRH)
Increased–> prolactin–> dis-inhibition (not inhibited) by dopamine
PP not really affected unless tumour affect hypothalamic function or inflammatory process involved
In which order are the hormones affected in hypopituitarism?
GH lost first (GHRH)–> short stature in children, reduced QoL in adults
LH/FSH second (GnRH)–> delayed puberty in children. loss of sexual characteristics in adults, loss of period in women (early sign)
TSH/ ACTH third (TRH, CRH)–> late feature of tumour
–> TSH–> low T hormones, weight gain, tiredness, slow pulse, Low T4 and Low TSH
–> ACTH–> low cortisol, tired, dizzy, low BP, low Na+
can be LIFE THREATENING!
What are the symptoms of growth hormone deficiency? Why is it difficult to diagnoses? What causes it? How is severe GH deficiency treated?
Symptoms in adults subtle
Decrease tolerance to exercise, decrease muscle strength, increased body fat, reduced sense of ‘well-being’
Severe prenatal deficiency-> hyperglycaemia and jaundice, poor growth and shorten stature
GH released in pulsative fashion
Cause in children generally idiopathic, specific gene mutations identified and autoimmune inflammation in some cases
Recombinant DNA technology to manufacture GH
What are the results of gonadotropin deficiency?
Hypogonadism
Lack of libido, infertility, oligomenorrhea or amenorrhea , impotence
What is hyperpituitarism?
Excess pituitary hormones production
Hypersecreting pituitary adenoma
Three main conditions: Prolactin excess, Growth hormone excess and ACTH excess
What is prolactinoma?
Prolactin-secreting pituitary tumour
large tumour–> macro-adenoma
small tumour–> micro-adenoma
Larger the tumour= higher the prolactin
What is hyperprolactinaemia? What causes it? What are the symptoms?
Abnormally high prolactin level
Prolactinoma (most common cause)
Symptoms
-Galactorrhoea (unexplained milk produciton)
-Gynecomastia (hard breast tissue)
-Hypogonadism (dimished activites of testes and ovaries)
-Amenorrhea (cessation of menstural cycle)
-Erectile dysfunction (men)
What normally causes high prolactin?
Physiological causes such as pregnancy, suckling, stress and exercise and drugs (antipsychotics and antidepressants)
Disinhibition of prolactin
–> compression of infindibulum prevent dopamine secretion (inhibits prolactin)
prolactin <5000–> disinhibition
prolactin >5000–> active prolactin secretion (prolactinoma)