03. Central Endocrine Glands

• the hypothalamus controls endocrine function via the pituitary gland. it responds to environmental and neural signals
• hormones ending in RH are released by the hypothalamus
• anterior pituitary hormones are regulated by hormones from the hypothalamus, while the posterior pituitary hormones are synthesised in the hypothalamus
• the pituitary releases trophic hormones - these don't have direct effects but bind to receptors on other organs
• anterior pituitary hormones = TSH, ACTH, LH, FSH, GH and prolactin
• posterior pituitary hormones = oxytocin and ADH
• lactotroph functional tumour = prolactinoma
• corticotroph functional tumour = cushings
• somatotroph functional tumour = acromegaly
• TSH, FSH and LH are glycoproteins, with an a and b subunit

  • the a subunit is common to all
• pituitary failure leads to secondary hypothyroidism while a pituitary tumour leads to secondary hyperthyroidism
• LH and FSH act through Gs GPCRs leading to increased cAMP and PKA activation
• ACTH is synthesised from POMC
• ACTH leads to cortisol production and is triggered by stress
• dopamine and somatostatin inhibit prolactin secretion
• VIP and TRH stimulate prolactin secretion
• prolactin increases milk production and is stimulated by suckling, sleep and stress
• growth hormone is stimulated by low glucose, exercise and sleep
• growth hormone directly increases blood glucose and causes bone and tissue growth
• growth hormone indirectly acts on the liver to release insulin like growth factors which cause cartilage growth
• ADH is stimulated by thirst/dehydration
• ADH deficiency leads to diabetes insipidus
• oxytocin stimulates contraction of smooth muscle in breast and uterus - this can be given to induce labour