Endocrine System

• Endocrine glands are groups of secretory

  cells surrounded by extensive networks of capillaries that

  facilitate diffusion of hormones from the secretory cells into the bloodstream.
• Homeostasis of the internal environment is maintained

  partly by the autonomic nervous system and partly by

  the endocrine system
• Growth hormone releasing hormone ➙ growth hormone (GH, somatotropin) ➙ most tissues and many organs
• Growth hormone release inhibiting hormone (GHRIH, somatostatin) ➙ GH inhibition, thyroid stimulating hormone (TSH) inhibition ➙ thyroid gland, pancreatic islets, most tissues
• Thyrotropin releasing hormone ➙ thyroid stimulating hormone ➙ thyroid glands
• Corticotropin releasing hormone ➙ adrenocorticotrophic hormone (ACTH) ➙ adrenal cortex
• Prolactin releasing hormone (PRH) ➙ Prolaction or prolactin (iactogenic hormone, PRL) ➙ breast
• Prolactin inhibiting hormone (dopamine, PIH) ➙ PRL inhibition ➙ Breast
• Luteinising hormone releasing hormone (LHRH) ➙ follicle stimulating hormone (FSH) ➙ ovaries and testes
• Gonadotrophin releasing hormone (GnRH) ➙ luteinising hormone (LH) ➙ ovaries and testes
• Growth hormone is a stress hormone
• T4 - thyroxine
• T3 - tri-iodothyronine