Hyposecretion of anterior pituitary hormones Flashcards
Give examples of anterior pituitary hormones
FSH/LH Prolactin GH TSH ACTH
What do levels of endocrine diseases mean?
If a defect lies in the adenohypophysis then it is a secondary endocrine disease - the level of the defect determines the category
E.g. endocrine gland is primary
Hypothalamus is tertiary
What is hypopituitarism and panhypopituitarism?
Decreased production of all adenohypophysial hormones
Congenital or acquired
What are the signs of panhypopituitarism?
Short stature and more
What investigations are conducted to diagnose panhypopituitarism
Hypoplastic adenohypophysis on MRI - underdeveloped
What are the types of acquired panhypopituitarism?
- tumours (hypothalamic(craniopharyngioma) or pituitary(adenoma, metasteses, cysts))
- radiation - hypothalamic/pituitary damage
- infection - meningitis
- traumatic brain injury - explosion
- infiltrative disease - neurosarcoidosis
- pituitary apoplexy - unconsciousness from haemorrhage
- peripartum infarction
During radiation which hormones is most and least likely to be affected?
GH - most vulnerable
TSH - resistant
What is Sheehan’s syndrome?
Infarcts pituitary upon giving birth
What does panhypopituitarism present with? (Specify which hormone causes each effect)
FSH/LH - secondary hypogonadism(gonad not problem the pituitary is), reduced libido, secondary amenorrhoea, erectile dysfunction
ACTH - secondary hypoadrenalism, fatigue
TSH - secondary hypothyroidism, fatigue, weight gain
What causes congenital panhypopituitarism and what does it result in?
RARE
due to mutations of transciption factor genes needed for normal pituitary development
Leads to deficiency of GH and at least another pituitary hormone
Which parts of the world is Sheehan’s syndrome common in?
less developed countries
How is Sheehan’s disease presented? (easily noticed and not well noticed)
Hard to notice – lethargy, anorexia, weight gain (TSH, ACTH, GH deficiency)
Easy to notice – failure of lactation (prolactin deficiency), failure to resume menstrual cycles post-delivery
What is pituitary apoplexy?
Dramatic presentation in patients with pre-existing pituitary adenomas (known or not known)
- Haemorrhage or a bleed
- Can be precipitated by anti-coagulants
What are the symptoms of pituitary apoplexy?
- severe sudden onset headache
- bitemporal hemianopia (pressing on the optic chiasm)
- diplopia (double vision)
- ptosis (drooping upper eyelid)
What are the ways in which hypopituitarism can be diagnosed?
Biochemical diagnosis
Radiological diagnosis- MRI can show if the sella turcica is empty for example
How are different hormones tested for through a biochemical diagnosis?
- Stimulated pituitary function tests
ACTH GH = ‘stress hormones’ – stress is defined as hypoglycaemia (<2.2mM glucose)
- An insulin-induced hypoglycaemia stimulates GH and ACTH (cortisol measured) release
- TRH (in injection) then stimulates TSH release and GnRH stimulates FSH and LH release
Why is it not useful to measure basal plasma concentrations of different hormones?
- cortisol is in small volumes and varies throughout the day
- T4/thyroxine has a long half-life (6 days) and so may take a while for it to fall
- FSH/LH is cyclical.
- GH/ACTH is pulsatile
What are the therapies for ACTH, TSH, FSH/LH and GH deficiency and how is effectiveness checked?
ACTH - hydrocortisone (cortisol)
TSH - thyroxine (T4)
LH/FSH (female) - E2 and progestagen (symtpoms improve)
LH/FSH - testosterone (symptoms improve and testosterone)
GH - GH (IGF1, growth in children)
What is the definition of short stature?
Children = <2 SDs from the mean.
Adults = less clear definition.
What are the causes of short stature?
Genetic – e.g. Downs, Turner’s, Prader-Willi syndromes
Emotional deprivation
Systemic disease
Malnutrition - Malabsorption – e.g. coeliac disease.
Endocrine disorders – e.g. Cushing’s, hypothyroidism, GH deficiency
Skeletal dysplasia – e.g. Achondroplasia, osteogenesis imperfecta
Summarise the main parts of the growth axis
Hypothalamus makes GHRH and SS
This causes GH release or inhibition
this acts on target tissues
It can also act on the liver to produce IGF1 and IGF2 which act on target tissues
PROBLEMS WITH THE HYPOTHALAMUS, LACK OF GH, GH RECEPTOR DEFECTS
Describe some of the different types of short stature
Dwarfism – achondroplasia
Mutation in Fibroblast Growth Factor Receptor 3 (FGF3). Abnormalities in growth plate chondrocytes that impairs linear growth resulting in an average sized trunk and short arms/legs.
Pituitary dwarfism – childhood GH deficiency
Prader Willi syndrome – GH deficiency secondary to hypothalamic dysfunction
Laron dwarfism – high local incidence, mutation in GH receptor treated with IGF-1 in childhood
How can short stature be diagnosed?
- A predicted height is calculated using parents heights and then the child’s length (later height) mapped against its weight is followed.
- If they fall below the lowest line, they often need referring to a paediatrician.
What are the causes of acquired GH deficiency in adults?
trauma, pituitary tumour/surgery and cranial radiotherapy
