Hyposecretion of anterior pituitary hormones Flashcards
Distinguish between primary, secondary and tertiary disease states relating to pituitary function
Hypothalamic disorder –> TERTIARY endocrine gland disease
Anterior pituitary disorder –> SECONDARY endocrine gland disease
Endocrine gland disorder, e.g. thyroid, gonads, adrenal cortex –> PRIMARY endocrine gland disease
Recall the individual pituitary hormone deficiency states that can occur
- Gonadotrophins (LH/FSH) –> hypogonadism
- Thyrotrophin (TRH) –> hypothyroidism
- Corticotrophin (ACTH) – hypoadrenocorticalism
- Somatotrophin (GH) deficiency
How are individual pituitary hormone deficiency states treated?
ACTH - hydrocortisone - check serum cortisol
TSH - thyroxine - check serum free T4
Women LH/FSH - HRT - symptom improvement, withdrawal bleeds
Men LH/FSH - testosterone - symptom improvement, serum testosterone
GH - GH - check IGF1, growth chart (children)
What are the signs of pan-hypopituitarism?
- Short stature
- Hypoplastic anterior pituitary gland on MRI
- Deficient in GH + 1 more AP hormone
What are the symptoms of pan-hypopituitarism?
Symptoms due to deficient hormones, depends on which hormones affected:
- FSH/LH: secondary hypogonadism - secondary amenorrhoea, reduced libido, erectile dysfunction
- ACTH - secondary hypoadrenalism (cortisol deficiency) - fatigue
- TSH - secondary hypothyroidism - fatigue, weight gain
What are the anterior pituitary hormones?
FSH/LH GH TSH ACTH Prolactin
What is Sheehan’s syndrome?
- Specific in women
- Post-partum hypopituitarism secondary to hypotension
- Develops acutely following post-partum haemorrhage resulting in pituitary infarction
- Blood loss results in vasoconstrictor spasm of hypophysial arters –> ischaemia of pituitary (which is enlarged during pregnancy) –> necrosis
What are the endocrine causes of short stature?
- Cushing’s
- Hypothyroidism
- GH deficiency (most caused by decreased GHRH production)
- Poorly controlled T1DM
What are the non-endocrine causes of short stature?
- Genetic (Down’s, Turner’s, Prader-Willi)
- Malabsorption (Coeliac)
- Systemic disease (CF, rheumatoid arthritis)
- Emotional deprivation (stress)
- Skeletal dysplasias (achrondroplasia, osteogenesis imperfecta)
How is short stature diagnosed in children?
2 standard deviations below mean height for same age and sex
What are the potential benefits of human growth hormone therapy in adults?
- Improved body composition
- Improved muscle strength and exercise capacity
- Normalisation of HDL-LDL balance - good for CVS
- Increased bone mineral content
- Improved psychological wellbeing and quality of life
What are the pharmacokinetic properties of human growth hormone?
Admin:
- s.c. or i.m.
- Daily or 4/5x week in the afternoon
- Adjust dose to size
- Maximal plasma conc in 2-6 hours
- Hepatic/renal metabolism
- Short half-life = 20 mins
- Long DOA as works on protein synthesis
- IGF I levels peak after around 20h
What are the symptoms of pituitary apoplexy?
- Severe sudden onset headache
- Visual field defect - compressed optic chiasm, bitemporal hemianopia
- Cavernous sinus involvement –> diplopa, ptosis
How is hypopituitarism diagnosed?
Biochemical diagnosis
- Basal plasma concentrations of pituitary or target endocrine gland hormones
- Stimulated pituitary function tests
- ACTH, GH = stress hormones
- Hypoglycaemia = ‘stress’
- Insulin-induced hypoglycaemia stimulates GH and ACTH release (cortisol measured)
- Give TRH to stimulate TSH release
- Give GnRH to stimulate FSH + LH release
What is the limitations of measuring basal plasma concentrations of pituitary or target endocrine gland hormones to diagnose hypopituitarism?
Interpretations may be limited:
- Undetectable cortisol - diurnal variation
- T4 - circulating t1/2=6 days
- FSH/LH - cyclical
- GH/ACTH - pulsatile
