9th February 2024

Posterior pituitary gland

Antidiuretic hormone (ADH) 

ADH is a nonapeptide that acts on the distal convoluted tubules and collecting ducts, resulting in increased water permeability and vasoconstriction. 

Its secretion is stimulated by increased serum osmolality, nausea, pain, hypoglycaemia, opiates and certain drugs (e.g., nicotine). Secretion is inhibited by reduced serum osmolality, alcohol and ANP. 

Oxytocin 

Oxytocin is a nonapeptide that acts on the uterus and breast tissue, resulting in uterine contraction and the milk ejection reflex. 

Labour stimulates its secretion (predominantly during the 2nd stage, especially in response to cervical dilation) and breast suckling.