Endocrine system

The endocrine system is a control system of ductless endocrine glands that secrete chemical messengers called hormones that circulate within the body via the bloodstream to affect distant organs. It does not include exocrine glands such as salivary glands, sweat glands and glands within the gastrointestinal tract.

Signal transduction of some hormones with steroid structure involves nuclear hormone receptor proteins that are a class of ligand activated proteins that, when bound to specific sequences of DNA serve as on-off switches for transcription within the cell nucleus. These switches control the development and differentiation of skin, bone and behavioral centers in the brain, as well as the continual regulation of reproductive tissues.

Diseases of the endocrine system are common, such as diabetes mellitus and thyroid disease. The field of medicine that deals with disorders of endocrine glands is endocrinology, a branch of the wider field of internal medicine.

Table of endocrine glands and the hormones secreted

In both sexes:

(starting from the head and going downwards)

• hypothalamus
  • thyrotropin-releasing hormone (TRH)
  • gonadotropin-releasing hormone (GnRH)
  • growth hormone-releasing hormone (GHRH)
  • corticotropin-releasing hormone (CRH)
  • somatostatin
  • dopamine

• pituitary gland
  • anterior lobe (adenohypophysis)
    • GH (human growth hormone)
    • PRL (prolactin)
    • ACTH (adrenocorticotropic hormone)
    • TSH (thyroid-stimulating hormone)
    • FSH (follicle-stimulating hormone)
    • LH (luteinizing hormone)
  • posterior lobe (neurohypophysis)
    • oxytocin
    • ADH (antidiuretic hormone)

• pineal gland
  • melatonin

• thyroid gland (thyroid hormones is a good writeup)
  • thyroxine (T4)
  • triiodothyronine (T3)
  • calcitonin

• parathyroid glands
  • parathyroid hormone (PTH)

• heart
  • atrial-natriuretic peptide (ANP)

• stomach and intestines
  • gastrin
  • secretin
  • cholecystokinin (CCK)
  • somatostatin
  • neuropeptide Y

• liver
  • insulin-like growth factor
  • angiotensinogen
  • thrombopoietin

• islets of Langerhans in the pancreas
  • insulin
  • glucagon
  • somatostatin

• adrenal glands
  • adrenal cortex
    • glucocorticoids – cortisol
    • mineralocorticoids – aldosterone
    • androgens (including testosterone)
  • adrenal medulla
    • adrenaline (epinephrine)
    • noradrenaline (norepinephrine)

• kidney
  • renin
  • erythropoietin (EPO)
  • calcitriol

• skin
  • calciferol (vitamin D₃)

• adipose tissue
  • leptin

In males only

• testes
  • androgens (testosterone)

In females only

• ovarian follicle
  • oestrogens
  • testosterone

• corpus luteum
  • progesterone

• placenta (when pregnant)
  • progesterone
  • human chorionic gonadotrophin (HCG)
  • human placental lactogen (HPL)

See also

• Target organ
• Receptors
• Releasing hormones
• Nervous system