Endocrine System: Glands and Hormones

Your body's endocrine system works like a chemical communication network. Various glands throughout your body release hormones directly into your bloodstream without using ducts. Think of hormones as text messages sent to specific parts of your body!

The pineal gland acts as your internal clock, secreting melatonin at night to help regulate your circadian rhythm $sleep-wake cycle$. Meanwhile, the pituitary gland serves as the "master gland," directing other glands to produce hormones. It has two parts: the anterior section produces growth hormone, while the posterior releases oxytocin and antidiuretic hormone (ADH) which controls your body's water balance.

Your thyroid gland in your throat produces T3/T4 hormones that regulate metabolism and calcitonin that lowers calcium levels. The nearby parathyroid glands do the opposite with PTH, raising blood calcium. Your pancreas maintains blood sugar balance by secreting insulin (which lowers blood sugar) and glucagon (which raises it).

Did you know? During the "fight-or-flight" response, your adrenal glands release adrenaline (epinephrine) that can temporarily give you extra strength, affect your bladder control, and even impact menstrual cycles!

The adrenal glands sit above your kidneys and have two parts: the cortex produces anti-inflammatory glucocorticoids, while the medulla releases epinephrine (adrenaline) during stress. For reproduction, ovaries produce estrogen for female characteristics, while testes make testosterone for male traits.

Hormones come in two main types: water-soluble $protein-based$ hormones like epinephrine that dock outside the cell and send messages to the nucleus, and lipid-soluble $fat-based$ hormones like testosterone, steroids, progesterone, and estrogen that can enter cells directly and affect DNA.