Of the endocrine glands, the hypothalamus and pituitary glands are of major importance since they act as the coordinating centers of the endocrine system. Show The hypothalamus is responsible for maintaining the body's internal balance (homeostasis) by stimulating or inhibiting major bodily functions such as the heart rate and blood pressure, body temperature, fluid and electrolyte balance, appetite and body weight, sleep cycle and function of the gastrointestinal track. The hypothalamus is also considered the master regulator of the endocrine system; Regulatory hormones secreted by the hypothalamus are transported by the hypophyseal-portal system to the anterior and posterior pituitary (Figure 2), prompting the release of secondary hormones that can affect various organ functions.  Figure 2. The hypophyseal-portal system Hormones typically bind to membrane or nuclear receptors of specific target glands/organs, which in turn release hormones that exert negative feedback control on the releasing sites. (Figure 3). Figure 3. Example of negative (in red) feedback inhibition: The hypothalamus secretes releasing factors that act on the pituitary gland to stimulate the release of trophic hormones. Trophic hormones act then on target organs (e.g., adrenal, thyroid or gonads), which in response produce other hormones/signals, shutting down the production of releasing or/and trophic hormones. The hypothalamus secretes various hormones that are then transported to the anterior pituitary (Figure 4):
Figure 4. Overview of hypothalamic and pituitary hormones and their actions The pituitary gland also secretes hormones in response to hypothalamic release hormones:
Supraoptic and paraventricular nuclei of the hypothalamus also secrete hormones that are transported to the posterior pituitary to be released into the circulation. These are:
Disorders of the hypothalamus can result in appetite, temperature and sleep disorders. As an example, hypothalamic obesity occasionally develops in response to major hypothalamic injury/damage affecting the centers of appetite regulation and energy balance. Hypothalamic obesity is characterized by an uninhibited eating disorder that often results in morbid obesity and can be associated with other obesity complications like diabetes, dyslipidemia, obstructive sleep apnea, mood disorder etc. Disorders of the hypothalamus and/or anterior pituitary can also result in hypopituitarism, including adrenal insufficiency (see adrenal disorders section), hypothyroidism (see thyroid disorders section), hypogonadism (see puberty and its disorders section), growth hormone deficiency (see growth disorders section) and prolactin deficiency (inability to lactate). Disorders of the posterior pituitary can result in diabetes insipidus and disorders pertaining to oxytocin deficiency (like inability to lactate, vaginal dryness, decreased libido etc.). The endocrine system is made up of glands that make hormones. Hormones are the body's chemical messengers. They carry information and instructions from one set of cells to another. The endocrine (pronounced: EN-duh-krin) system influences almost every cell, organ, and function of our bodies. What Does the Endocrine System Do?
Too much or too little of any hormone can harm the body. Medicines can treat many of these problems. What Are the Parts of the Endocrine System?While many parts of the body make hormones, the major glands that make up the endocrine system are the:
The pancreas is part of the endocrine system and the digestive system. That's because it secretes hormones into the bloodstream, and makes and secretes enzymes into the digestive tract. Hypothalamus: The hypothalamus (pronounced: hi-po-THAL-uh-mus) is in the lower central part of the brain. It links the endocrine system and nervous system. Nerve cells in the hypothalamus make chemicals that control the release of hormones secreted from the pituitary gland. The hypothalamus gathers information sensed by the brain (such as the surrounding temperature, light exposure, and feelings) and sends it to the pituitary. This information influences the hormones that the pituitary makes and releases. Pituitary: The pituitary (pronounced: puh-TOO-uh-ter-ee) gland is at the base of the brain, and is no bigger than a pea. Despite its small size, the pituitary is often called the "master gland." The hormones it makes control many other endocrine glands. The pituitary gland makes many hormones, such as:
The pituitary also secretes endorphins (pronounced: en-DOR-fins), chemicals that act on the nervous system and reduce feelings of pain. The pituitary also secretes hormones that signal the reproductive organs to make sex hormones. The pituitary gland also controls and the menstrual cycle in women. Thyroid: The thyroid (pronounced: THY-royd) is in the front part of the lower neck. It's shaped like a bow tie or butterfly. It makes the thyroid hormones thyroxine (pronounced: thy-RAHK-sin) and triiodothyronine (pronounced: try-eye-oh-doe-THY-ruh-neen). These hormones control the rate at which cells burn fuels from food to make energy. The more thyroid hormone there is in the bloodstream, the faster chemical reactions happen in the body. Thyroid hormones are important because they help kids' and teens' bones grow and develop, and they also play a role in the development of the brain and nervous system. Parathyroids: Attached to the thyroid are four tiny glands that work together called the parathyroids (pronounced: par-uh-THY-roydz). They release parathyroid hormone, which controls the level of calcium in the blood with the help of calcitonin (pronounced: kal-suh-TOE-nin), which the thyroid makes. Adrenal Glands: These two triangular adrenal (pronounced: uh-DREE-nul) glands sit on top of each kidney. The adrenal glands have two parts, each of which makes a set of hormones and has a different function:
Pineal: The pineal (pronounced: pih-NEE-ul) body, also called the pineal gland, is in the middle of the brain. It secretes melatonin (pronounced: meh-luh-TOE-nin), a hormone that may help regulate when you sleep at night and when you wake in the morning. Reproductive Glands: The gonads are the main source of sex hormones. Most people don't realize it, but both guys and girls have gonads. In guys the male gonads, or testes (pronounced: TES-teez), are in the scrotum. They secrete hormones called androgens (pronounced: AN-druh-junz), the most important of which is (pronounced: tess-TOSS-tuh-rone). These hormones tell a guy's body when it's time to make the changes associated with puberty, like penis and height growth, deepening voice, and growth in facial and pubic hair. Working with hormones from the pituitary gland, testosterone also tells a guy's body when it's time to make sperm in the testes. A girl's gonads, the ovaries (pronounced: OH-vuh-reez), are in her pelvis. They make eggs and secrete the female hormones (pronounced: ESS-truh-jen) and (pronounced: pro-JESS-tuh-rone). Estrogen is involved when a girl starts puberty. During puberty, a girl will have breast growth, start to accumulate body fat around the hips and thighs, and have a growth spurt. Estrogen and progesterone are also involved in the regulation of a girl's menstrual cycle. These hormones also play a role in pregnancy. Pancreas: The pancreas (pronounced: PAN-kree-us) makes insulin (pronounced: IN-suh-lin) and glucagon (pronounced: GLOO-kuh-gawn), which are hormones that control the level of glucose, or sugar, in the blood. Insulin helps keep the body supplied with stores of energy. The body uses this stored energy for exercise and activity, and it also helps organs work as they should. What gland does hypothalamus affect?The hypothalamus helps control the pituitary gland and regulates many body functions. The central nervous system comprises the brain and spinal cord. The peripheral nervous system includes all peripheral nerves. The hypothalamus is a highly complex structure in the brain that regulates many important brain chemicals.
What gland is most controlled by the hypothalamus?The gland is attached to a part of the brain (the hypothalamus) that controls its activity. The anterior pituitary gland is connected to the brain by short blood vessels. The posterior pituitary gland forms part of the brain and secretes hormones directly into the bloodstream under the command of the brain.
What gland secretes hypothalamic releasing hormones?Anterior pituitary. |
