hormones of posterior pituitary gland

what 2 hormones dies posterior pituitary gland secrete

• vasopressin (ADH or AVP)

• oxytocin

where are posterior pituitary hormones synthesised

in hypothalamus - supraoptic and paraventricular nuclei

how do posterior pituitary hormones reach the bloodstream

they are transported down unmyelinated nerve fibres and released directly into circulation

role of vasopressin

encourages reabsorption of water from distal convoluted tubules and collecting ducts of kidney so conserving body fluid

what effect does vasopressin have on blood pressure

at high concentrations, it causes vasoconstriction and increases systemic blood pressure

what is the most important stimulus for vasopressin release

increased plasma osmolarity detected by hypothalamic osmoreceptors

how does blood volume or pressure affect vasopressin release

low blood volume or pressure increases vasopressin release due to reduced baroreceptor stimulation

which factors increase vasopressin release

• severe pain

• fear

• nausea

• general anaesthesia

• nicotine

• noradrenaline

which substance inhibits vasopressin release

alcohol

summary of control of vasopressin (ADH) release

what condition results from vasopressin hyposecretion

diabetes insipidus

what are the features of diabetes insipidus

excessive production of large volumes of dilute urine

how is diabetes insipidus treated

synthetic vasopressin (argipressin) or desmopressin (intranasal)

what condition results from vasopressin hypersecretion

Schwartz–Bartter syndrome (SIADH) - caused by small cell lung carcinoma

what are the key features of Schwartz–Bartter syndrome

• excessive water retention

• low serum osmolarity

• hyponatraemia

• concentrated urine

how is vasopressin hypersecretion treated

• tumour removal if possible

  • tumours are those that produce ADH inappropriately leading to hypersecretion

  • ectopic tumours so located outside pituitary

• use of AVP anatagonist demeclocycline

what is the primary role of oxytocin in childbirth

stimulates rhythmic contractions of uterine smooth muscles

what is oxytocins role in lactation

stimulates milk ejection in response to suckling

is oxytocin essential for initiation of labour

no, it contributes but not essential

how is oxytocin release regulated

by neurogenic positive feedback from sensory stimulation of the nipple (suckling) and uterus (labour)

true or false: disorders of oxytocin secretion are common

false - rare

what are the clinical uses of synthetic oxytocin

induction of labour and stimulation of uterine contractions after childbirth for placental delivery