L2 HPA axis Flashcards
Briefly explain the HPA axis
Stress (both psychological and physical) leads to CRH release from hypothalamus, which stimulates ACTH release from pituitary and subsequent cortisol release from adrenal cortex. This is known as the hypothalamic-pituitary-adrenal axis.
What are neuroendocrine mediators?
Substances that function as neurotransmitters, neural hormones and classic hormones e.g. oxytocin, ADH, dopamine, somatostatin
Role of ADH/vasopressin
- osmoregulation
- regulation of ECF volume
Role of oxytocin
regulation of uterine contractions and milk ejection
What is the anterior and posterior hypothalamus involved in?
thermoregulation
Posterior pituitary hormones
- arginine vasopressin (AVP)/ADH
- oxytocin
Which hormone is most commonly secreted in excess amounts by pituitary adenomas?
Prolactin (PRL)
Pituitary and hypothalamic disorders
- Pituitary hypersecretion
- Pituitary insufficiency
- Hypopituitarism
Which patients usually have elevated PRL?
those with hypothalamic disorders and pituitary stalk compression
PRL measurement should be performed in patients presenting with…
- galactorrhoea
- gonadal dysfunction
- secondary gonadotropin deficiency
- enlargement of the sella turcica
Hypersecretion of GH can lead to?
acromegaly
Hypersecretion of ACTH can lead to?
Cushing disease
What is panhypopituitarism?
the lack of all pituitary hormones
- present in <20% of patients with pituitary adenomas
What is the earliest clinical manifestation of a pituitary adenoma in adults?
Hypogonadism, secondary to elevated levels of PRL, GH, or ACTH and cortisol
Hypogonadism in patients with a pituitary adenoma is due to…
interference with GnRH secretion, rather than destruction of anterior pituitary tissue
What is done first to exclude primary gonadal failure in patients with hypogonadism?
screened with FSH and LH measurements
What is the most frequent clinical presentation of hypothalamic-pituitary dysfunction in children?
short stature
- GH deficiency should be considered in these children
TSH or ACTH deficiency is relatively unusual and if present, usually indicates __.
panhypopituitarism
What are commonly associated with secondary hypothyroidism or hypoadrenalism?
panhypopituitarism and large pituitary tumours
What are the most common pituitary tumours in adults?
Prolactinomas
What is hypopituitarism manifested by?
diminished or absent secretion of one or more pituitary hormones
Hypopituitarism is either
- a primary event caused by destruction of the anterior pituitary gland, or
- a secondary phenomenon resulting from deficiency of hypothalamic stimulatory factors normally acting on the pituitary
In general, acquired loss of anterior pituitary function follows what sequence?
GH, LH/FSH, TSH, ACTH, PRL