Endocrinology 1 - Hyposecretion of Anterior Pituitary Hormones Flashcards
List the anterior pituitary hormones
- FSH/LH
- Prolactin
- GH
- TSH
- ACTH
What results in secondary hypothyroidism?
- Lack of production of the anterior pituitary hormone (TSH)
- Thyroid gland is functional
What results in primary hypothyroidism?
- Disorder in the thyroid gland
- Results in lack of production of T3 and T4
Define hypopituitarism
- Decreased production of all anterior pituitary hormones (panhypopituitarism)
- Or can be decreased production of specific hormones
- May be congenital or acquired
Congenital panhypopituitarism
- Cause
- Symptoms
- Usually due to mutations of transcription factor genes needed for normal anterior pituitary development (eg PROP1 mutation)
- Deficient in GH and at least 1 more anterior pituitary hormone
- Short stature
- Hypoplastic anterior pituitary gland on MRI
List the causes of acquired panhypopituitarism
- Hypothamic tumours (craniopharyngiomas) or pituitary tumours (adenomas, metastases and cysts)
- Radiation (hypothamic/pituitary damage, GH most vulnerable and TSH resistant)
- Infection (eg. meningitis)
- Traumatic brain injury
- Infiltrative disease (pituitary stalk - neurosarcoidosis)
- Inflammatory (hypophystitis)
- Pituitary apoplexy (haemorrhage)
- Peri-partum infarction (sheenans syndrome)
Describe the presentation of panhypopituitarism (Simmonds disease)
FSH/LH causes
- Secondary hypogonadism
- Reduced libido
- Secondary amenorrhoea
- Erectile dysfunction
ACTH causes
- Secondary hypoadrenalism
- Fatigue
TSH causes:
- Secondary hypothyroidism
- Fatigue
What is Sheenans syndrome?
- Post-partum hypopituitarism secondary to hypotension
- Less common in developed countries
- Anterior pituitary enlarges in pregnancy (due to lactotroph cell enlargement), and post partum haemorrhage leads to pituitary infarction
Describe the presentation of Sheehans syndrome
- Lethargy anorexia and weight loss (TSH, ACTH and GH deficiency)
- Failure of lactation (Prolactin deficiency)
- Failure to resume menses post- delivery
- Posterior pituitary usually not affected
What is pituitary apoplexy?
- Intra-pituitary haemorrhage or infarction
- Often dramatic presentation in patients with pre-existing pituitary tumours
- May be first presentation of adenoma
- Precipitated by anti-coagulants
What are the symptoms of pituitary apoplexy?
- Severe sudden onset headache
- Visual field defect (bitemporal hemianopia)
- Cavernous sinus involvement may lead to diplopia or ptosis
How is biochemical diagnosis of hypopituitarism performed?
- Basal plasma concentrations of pituitary or target endocrine gland hormones (although may not be appropriate as levels are not constant)
- Stimulated pituitary function tests (ACTH/GH stimulated by hypoglycaemia, so insulin is used. TRH and GnRH can be used for TSH and FSH and LH)
How is radiological diagnosis of hypopituitarism performed?
Pituitary MRI (may reveal haemorrhage or adenoma)
List the drugs used in hormone replacement therapy in hypopituitarism
- ACTH needs replacement of hydrocortisone (serum cortisol monitored)
- TSH thyroxine replacement (serum free T4)
- LH/FSH HRT in women, testosterone in men (symptom improvement)
- GH needs GH administration (monitor IGF1 or growth in children)
What are the effects of growth hormone deficiency?
- Short stature in children
- Less clear in adults
List the causes of short stature
- Genetic (Downs, Turners, Prader Willi)
- Emotional deprivation
- Systemic disease (CF or arthritis)
- Malnutrition
- Malabsorption (coeliac)
- Endocrine disorders (Cushings, Hypothyroidism, GH deficiency)
- Skeletal dysplasias (Achondroplasia, osteogenesis imperfecta)
List the different causes of short stature in children, relating to the growth axis
- Prader Willi affects hypothalamus
- Lack of GH results in pituitary dwarfism
- Laron dwarfism is due to GH receptor defect at the liver
What is achondroplasia (cause, characteristics)?
- Mutation in FCF3 (fibroblast growth factor receptor 3)
- Abnormality in growth plate chondrocytes
- Average size trunk with short arms and legs
- Not a pituitary disorder
How is short stature diagnosed?
- Using mid parental height
- Predicted adult height based on the mothers and fathers height
List the causes of acquired GH deficiency in adults
- Trauma
- Pituitary tumour
- Pituitary surgery
- Cranial
- Radiotherapy
How is GH deficiency diagnosed?
- Random GH is not useful as it is pulsatile
- Stimulation test is used (GHRH and arginine, insulin, glucagon or exercise)
Describe the preparation and administration of growth hormone therapy
- Uses human recombinant GH
- Administered daily by subcutaneous injection
- Dose adjusted based on IGF1
List the signs and symptoms of GH deficiency in adults
- Reduced lean mass, increased adiposity and increased waist to hip ratio
- Reduced muscle strength and bulk
- Decreased plasma HDL and increase LDL
- Impaired psychological wellbeing
List the potential benefits of GH therapy in adults
- Improved body composition (decreased waist circumference and visceral fat)
- Improved muscle strength and exercise capacity
- Higher HDL and lower LDL
- Increased bone mineral density
- Improved psychological well-being and quality of life
List the potential risks of GH therapy in adults
- Increased cancer risk (no data to support this)
- Expensive (£42K)
Describe the growth axis
- GHRH is released from the hypothalamus which stimulates growth hormone release from the anterior pituitary
- Somatostatin inhibits growth
- GH binds to liver cells and releases IGF1 and IGF2
