Other Hormones and their effects

• The endocrine system has three minor peripheral glands:

  • pineal gland
  • thymus
  • gonads
• Pineal gland - It is a small pinecone-shaped endocrine gland situated in the mid-region of the brain. 
• The pineal gland is primarily composed of masses of neuroglia and secretory cells called pinealocytes.
• The pineal gland secretes the hormone melatonin.
• Melatonin controls the body’s biological clock.
• Melatonin - It regulates the sleep-wake cycle.
• Melatonin follows a rhythmic pattern based on visual input:

  • low secretion at day and high secretion at night
• Melatonin concentration in the blood increases to up to tenfold during sleep.
• Melatonin is secreted more in darkness to promote sleepiness.
• • Melatonin is a potent antioxidant for it provides protection from the damaging effects of oxygen-free radicals.
• Melatonin levels are higher in children and decrease with age.
• Thymus - It is a mixed-function organ of the immune system and the endocrine system.
• Thymus - It is located behind the sternum between the lungs.
• Thymus produces different hormones, thymosin being the most prominent.
• • Thymosin contributes to the maturation of T lymphocytes or  T cells.
• T lymphocytes - They are WBCs that destroy microbes and foreign bodies in the internal environment.
• T lymphocytes - They also help destroy infected or cancerous cells. 
• • Thymus has been shown to retard the process of aging. 
• • Thymus gradually becomes smaller and less important as a person matures.
• Gonads, the organs that produce sex cells
• Gonads:

  • Testes - males
  • Ovaries - females
• Gonads - They are considered mixed-function organs because of their roles in reproduction.
• The ovaries are paired, oval-shaped structures located in the pelvic region.
• Each ovary synthesizes two steroid hormones: 

  • estrogen
  • progesterone
• Estrogen constitutes to estradiol, estrone, and estriol.
• Estradiol is the primary estrogen produced during a female’s reproductive years.
• Estriol plays a more important role during pregnancy.
• • Estrone is more prominent after menopause.
• • Estrogen contributes to the development of secondary sex characteristics in females.
• Estrogen - It promotes the development of follicles during the menstrual cycle. 
• Estrogen - It initiates and promote the growth of breasts and uterus.
• • Progesterone maintains the lining of the uterus for a possible pregnancy.
• Progesterone has also been shown to have antidepressant function.
• Progesterone - It also helps in the promotion of fat use for energy, regulation of blood sugar levels, and normalizing blood clotting. 
• The testes are oval glands in males that are housed within the scrotum.
• Scrotum - bag of skin that holds the testicles
• The main hormone produced and released by testis is the testosterone.
• Testes - It is the male sex hormone.
• • Testosterone helps the testes to descend outside the body before birth, because the abdominal temperature is not good for sperm production.
• Testosterone triggers the appearance of male secondary features like beard growth.