adrenocorticotropic hormone

Examples of adrenocorticotropic hormone in the following topics:

• Overview of the Pituitary Gland

  • The pituitary gland is connected to the hypothalamus and secretes nine hormones that regulate body homeostasis.
  • The pituitary gland secretes hormones that regulate body homeostasis.
  • Thyroid-stimulating hormone (TSH)- induces the thyroid to produce hormones that regulate metabolism
  • Adrenocorticotropic hormone (ACTH)- increases production of stress hormones by the adrenal glands
  • The posterior pituitary does not produce any hormones of its own, rather, it stores and secretes two hormones made in the hypothalamus:

• The Stress Response

  • The paraventricular nucleus of the hypothalmus contains neuroendocrine neurons which synthesize and release vasopressin—a hormone which acts in the HPA axis as a vasoconstrictor—and corticotropin releasing hormone (CRH).
  • These two hormones regulate the anterior lobe of the pituitary gland, stimulating the release of adrenocorticotropic hormone (ACTH), also known as corticotropin.
  • ACTH acts on the adrenal cortices which produce glucocorticoid hormones, like cortisol, which is a stress hormone which exerts many effects throughout the body.
  • Researchers have hypothesized that the hormonal changes brought on by stress may contribute to the neural atrophies seen in many neurodegenerative disease states.

• Epinephrine and Norepinephrine

  • As a hormone and neurotransmitter, epinephrine acts on nearly all body tissues.
  • Binding to α-adrenergic receptors inhibits insulin secretion by the pancreas, stimulates glycogenolysis (the breakdown of glycogen) in the liver and muscle, and stimulates glycolysis (the metabolic pathway that converts glucose into pyruvate) in muscle. β-Adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue.
  • It is the hormone and neurotransmitter most responsible for vigilant concentration in contrast to its most-chemically-similar hormone, dopamine, which is most responsible for cognitive alertness.
  • They are the flight/fight hormones that are released when the body is under extreme stress.
  • These hormones go one step further and trigger the renin-angiotensin-aldosterone system, the hormone system that regulates blood pressure and water (fluid) imbalance.

• Adrenal Gland Disorders

  • Adrenal insufficiency is a condition in which the adrenal glands, located above the kidneys , do not produce adequate amounts of steroid hormones, primarily cortisol, but may also include impaired aldosterone production which regulates sodium, potassium, and water retention.
  • Adrenal insufficiency can also occur when the hypothalamus or the pituitary gland, both located at the base of the skull, does not make adequate amounts of the hormones that assist in regulating adrenal function.
  • This is called secondary adrenal insufficiency and is caused by lack of production of adrenocorticotropic hormone (ACTH) in the pituitary gland or lack of corticotropin-releasing hormone (CRH) in the hypothalamus.

• The Endocrine System and Stress

  • The hypothalamus contains neurons that synthesize and secrete vasopressin and corticotropin-releasing hormone (CRH).
  • These two hormones travel through blood to the anterior pituitary, where they cause the secretion of stored adrenocorticotropic hormone (ACTH).
  • This causes a negative feedback cycle in which the steroids inhibit the hypothalamus and the pituitary gland, and it also causes the adrenal gland to produce the hormones epinephrine (also known as adrenaline) and norepinephrine.
  • Stress hormone release tends to decline gradually after a stressor occurs.
  • In post-traumatic stress disorder there appears to be lower-than-normal cortisol release, and it is thought that a blunted hormonal response to stress may predispose a person to develop PTSD.

• Hypothalamic-Pituitary Axis

  • The anterior pituitary produces seven hormones: growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), melanin-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH).
  • Anterior pituitary hormones are sometimes referred to as tropic hormones because they control the functioning of other organs.
  • While these hormones are produced by the anterior pituitary, their production is controlled by regulatory hormones produced by the hypothalamus.
  • These regulatory hormones can be releasing hormones or inhibiting hormones, causing more or less of the anterior pituitary hormones to be secreted.
  • Negative feedback then regulates how much of these regulatory hormones are released and how much anterior pituitary hormone is secreted.

• Pituitary Gland Disorders

  • The hypothalamus secretes a number of hormones, often according to a circadian rhythm, into blood vessels that supply the anterior pituitary; most of these are stimulatory (thyrotropin-releasing hormone, corticotropin-releasing hormone, gonadotropin-releasing hormone and growth hormone-releasing hormone), apart from dopamine, which suppresses prolactin production.
  • In response to the releasing hormone rate, the anterior pituitary produces its hormones (TSH, ACTH, LH, FSH, GH) that stimulate effector hormone glands in the body, although prolactin acts directly on the breast gland.
  • Adrenocorticotropic hormone (ACTH) deficiency leads to adrenal insufficiency, a lack of production of glucocorticoids such as cortisol by the adrenal gland.
  • Measurement of ACTH and growth hormone usually requires dynamic testing, whereas the other hormones (LH/FSH, prolactin, TSH) can typically be tested with basal levels.
  • Generally, the finding of a combination of a low pituitary hormone together with a low hormone from the effector gland is indicative of hypopituitarism.

• The Anterior Pituitary

  • Adrenocorticotropic hormone, also known as ACTH, is a polypeptide whose target is the adrenal gland.
  • Thyroid-stimulating hormone, also known as TSH, is a glycoprotein hormone that affects the thyroid gland and the secretion of thyroid hormones.
  • Follicle-stimulating hormone, abbreviated to FSH, is a glycoprotein hormone that targets the gonads and effects the growth of the reproductive system.
  • Luteinizing hormone, also known as LH, or ICSH is a glycoprotein hormone that also targets the gonads to effect sex hormone production.
  • Hormone secretion from the anterior pituitary gland is regulated by hormones secreted by the hypothalamus.

• Hormonal Regulation of Stress

  • Stressful stimuli cause the hypothalamus to signal the adrenal medulla (which mediates short-term stress responses) via nerve impulses, and the adrenal cortex, which mediates long-term stress responses via the hormone adrenocorticotropic hormone (ACTH), which is produced by the anterior pituitary.
  • Interactions of the endocrine hormones have evolved to ensure the body's internal environment remains stable.
  • Instead, other hormones come into play.
  • The adrenal cortex is stimulated by ACTH to release steroid hormones called corticosteroids.
  • These hormones target the breakdown of fat into fatty acids in the adipose tissue.

• How the Body Responds to Stress

  • When presented with stress, the body responds by releasing hormones that will prepare it for the fight-or-flight response.
  • When a threat or danger is perceived, the body responds by releasing hormones that will prepare it for the fight-or-flight response.
  • Stressful stimuli cause the hypothalamus to signal the adrenal medulla (which mediates short-term stress responses) via nerve impulses, and the adrenal cortex (which mediates long-term stress responses) via the hormone adrenocorticotropic hormone (ACTH), which is produced by the anterior pituitary.
  • When presented with a stressful situation, the body responds by calling for the release of hormones that provide a burst of energy.
  • Additionally, these hormones increase oxygen availability to cells by increasing the heart rate and dilating the bronchioles.