Hyposecretion of anterior pituitary hormones Flashcards
Lecture is different from notes
What are the anterior pituitary hormones?
Gonadotrophins (FSH/LH) Prolactin ACTH GH TSH
Define primary, secondary and tertiary gland disease?
Primary gland disease is where the gland producing the primary hormone is affected
Secondary gland disease is where the anterior pituitary gland producing the anterior pituitary hormone is affected
Tertiary is disorder in the hypothalamus
Primary hypothyroidism is a problem with the thyroid gland so you will have a high levels of TSH but low levels of thyroxine. Secondary hypothyroidism is a problem with the anterior pituitary gland so you will get low levels of TSH even though the thyroid may be functioning fine.
Define panhypopituitarism
Decreases production of all anterior pituitary hormones or of a specific hormone
Sometimes called Simmond’s disease
What categories of panhypopituitarism is there?
Congenital or Acquired
Describe congenital panhypopituitarism
Rare; can be as a result of a mutation in the transcription factors required for the normal growth and development of the anterior pituitary gland e.g PROP1 mutation.
Often people with congenital panhypopituitarism will be deficient in GH and another anterior pituitary hormone resulting in short stature and an underdeveloped anterior pituitary gland. Hypoplastic
Describe acquired panhypopituitarism
Caused by damage to the anterior pituitary gland:
tumours - hypothalamic or pituitary (craniopharyngiomas, adenomas or metastases)
Radiation - causes damage. GH is most affected by radiation. TSH is relatively resistant
Infection - meningitis
Inflammatory - hypophysitis
Inflitrative disease - often involves the pituitary stalk e.g neurosarcoidosis
Traumatic brain injury
Pituitary apoplexy - haemorrhage (or less commonly infarction
Peri-partum infarction (Sheehan’s syndrome)
Describe the symptoms of panhypopituitarism
The symptoms can vary depending on the hormones you are lacking. Mainly due to decreased function of the thyroid, gonads and adrenal glands
FSH/LH - secondary hypogonadism; reduced libido, erectile dysfunction and secondary ammenorrhoea
ACTH - Produces cortisol, high levels in the morning so it related to tiredness. Fatigue
TSH - fatigue
Describe Sheehan’s syndrome
During pregnancy the anterior pituitary gland swells and gets bigger because there is increased production of prolactin which is required for lactation. After birth if you get a post-partum haemorrhage the BP can drop very quickly meaning not enough blood is supplied to the enlarged pituitary resulting in an pituitary infarction. Pituitary ischaemia occurs then necrosis. Very fast
What is the presentation of Sheehan’s sydrome?
Lethargy, anorexia, weight loss - TSH/ACTH/GH deficiency. Not making enough thyroxine and cortisol = low energy. Low levels of cortisol = loss of weight and lethargic.
Failure of lactation - No more prolactin produced which means lactation can’t occur. No lactation after birth = big sign that it might be sheehan’s syndrome
Failure to resume menstruation post-delivery - FSH and LH deficiency would mean secondary ammenorrhea
Describe pituitary apoplexy
A pituitary apoplexy is an intra-pituitary haemorrhage or infarction - can be precipitated by anticoagulants. This often occurs with patients who have existing pituitary adenomas. Patients with pituitary apoplexy experience severe onset of headaches. If the tumour is large enough it can compress the optic chaisma resulting in bitemporal hemianopia. Blood entering the cavernous sinus can also compress the optic nerves causing diplopia (IV, VI) and ptosis (III)
How can you diagnose hypopituitarism?
Biochemical diagnosis
1) Measure basal plasma concentrations of pituitary or target endocrine gland hormones. However you need to take multiple measurements as the hormones are pulsatile depending on the time of day. Cortisol is highest in the morning
FSH/LH - cyclical
GH/ACTH - pulsatile
2) Stimulated (‘Dynamic’) pituitary function tests. Simulate ‘stress’ in the body to test for ACTH (specifically cortisol can’t measure ACTH) and GH. This can be done by making the body hypoglycaemic. make the blood glucose level below 2.2mM. As a result the anterior pituitary gland will produce lots of ACTH and GH in response to try and increase blood glucose.
Insulin can be used to induce hypoglycaemia. TRH can also be given to stimulate TSH release which can be measured. GnRH as well.
Radiological diagnosis - reveals specific pituitary pathology
1) Haemorrhage (apoplexy)
2) Adenoma
3) Empty sella - rim of pituitary tissue
What hormone can you not replace?
Prolactin - although the effects of prolactin deficiency aren’t that bad
What are the replacement hormones for ACTH, TSH, LH/FSH in men and women and GH? How can you check that the replacements have worked?
ACTH - hydrocortisone - Serum cortisol
TSH - Thyroxine - serum free T4
Woman LH/FSH - oestrogen up until the age of 50 (approximate age for menopause). If they have a uterus progesterone as well to prevent endometrial hyperplasia. - Improvement of mood and withdrawal bleeds
Men LH/FSH - Testosterone - measure serum testosterone and improvement of symptoms
GH - GH - IGF1, growth chart (children)
What are the effects of somatotrophin deficiency?
In children - short stature
In adults - effects are less clear
What are the causes of short stature?
Genetics - Down's, turners, Prader Willi Emotional deprivation Systemic disease - cystic fibrosis Malnutrition Malabsorption - coeliac disease Endocrine disorders - cushing's syndrome Skeletal dysplasia
