Pituitary Gland

The pituitary gland is a gland of the endocrine system which is about the size of a pea and extends off the bottom of the hypothalamus in a central location in the brain. 垂体是内分泌系统的一个腺体，大小约似豌豆，位于大脑中央位置，从下丘脑底部延伸出来。 "Hormones secreted from the pituitary gland help to control growth, blood pressure, energy management, all functions of the sex organs, thyroid glands and metabolism as well as some aspects of pregnancy, childbirth, breastfeeding, water/salt concentration at the kidneys, temperature regulation and pain relief." 由垂体分泌的激素有助于控制生长、血压、能量管理、性器官的所有功能、甲状腺腺体和代谢，以及怀孕、分娩、哺乳、肾脏的水盐浓度调节、体温调节和止痛。

The pituitary gland consists of two distinct lobes called the anterior and posterior pituitary. Both of them are regulated by the hypothalamus. The anterior pituitary produces hormones used in the reproductive process. It produces Follicle-stimulating hormone (FSH) and lutinizing hormone (LH) which stimulate production of sperm and testosterone in males and of eggs, estrogen, and progesterone in females.

The anterior pituitary gland interacts with the thyroid by producing the thyroid-stimulating hormone (TSH) which stimulates the thyroid to release its hormones.

The anterior pituitary gland also interacts with the adrenal gland by producing the adrenocorticotropic hormone (ACTH) to cause it to release its hormones.

The anterior pituitary gland also produces some hormones that do not interact with other endocrine glands:

• Prolactin helps stimulate the development of the mammary glands during pregnancy. These glands are classified as exocrine glands.
  泌乳素有助于促进妊娠期间乳腺的发育。这些腺体属于外分泌腺。
• Endorphins inhibit the perception of pain by binding to certain receptors in the brain.
  内啡肽通过与大脑中的某些受体结合，抑制对疼痛的感知。
• Melanocyte-stimulating hormone (MSH) stimulates the synthesis of the skin pigment melanin.
  黑素细胞刺激激素（MSH）促进皮肤色素黑色素的合成。
• Growth hormone acts on all the body's cells, regulating the body's growth.
  • Increases protein synthesis, fat utilization, and the storage of carbohydrates
    增加蛋白质合成、脂肪利用和碳水化合物的储存
  • Stimulates bone growth during maturation
    • Produces much of the normal variation in size of adult
      产生成年个体大小的大部分正常变异
    • Deficiency in production of the hormone leads to dwarfism, excess leads to gigantism.
      激素分泌不足会导致侏儒症，分泌过多则会导致巨人症。
    • Lifelong secretion helps to regulate metabolism of protein, fat and sugar.
      持续分泌有助于调节蛋白质、脂肪和糖的代谢。
    在成熟过程中刺激骨生长
  生长激素作用于身体的所有细胞，调节身体的生长。

The posterior pituitary acts in concert with the hypothalamus to release two peptide hormones that are synthesized in the hypothalamus. These two hormones are transported to the pituitary where they are transferred to capillary beds and travel in the bloodstream to their destinations. The antidiuretic hormone (ADH) increases the permeability to water of the collecting ducts of the nephrons of the kidney, causing water to be reabsorbed from the urine and retained in the body. This process acts as a negative feedback loop to control the content of water in the blood.

The hormone oxytocin, synthesized in the hypothalamus and distributed in the blood by the pituitary, aids in lactation by nursing mothers by causing muscles in the breast to contract. This ejects milk from the saclike milk glands into the nipples. Oxytocin also causes contraction of the muscles of the uterus during childbirth. Oxytocin may also affect male reproductive behavior by causing contraction of the sperm-carrying tubes, as observed in several animal species.