{"id":4334,"date":"2017-03-28T21:28:03","date_gmt":"2017-03-28T21:28:03","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology2\/?post_type=chapter&p=4334"},"modified":"2017-07-05T17:27:01","modified_gmt":"2017-07-05T17:27:01","slug":"types-of-hormones","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-wmopen-biology2\/chapter\/types-of-hormones\/","title":{"raw":"Types of Hormones","rendered":"Types of Hormones"},"content":{"raw":"

Identify different types of hormones and explain the regulation of hormone production<\/h2>\r\nAlthough there are many different hormones in the human body, they can be divided into three classes based on their chemical structure: lipid-derived, amino acid-derived, and peptide (peptide and proteins) hormones. One of the key distinguishing features of lipid-derived hormones is that they can diffuse across plasma membranes whereas the amino acid-derived and peptide hormones cannot.\r\n
\r\n

Learning Objectives<\/h3>\r\n
    \r\n \t
  • Explain the role of lipid-derived hormones in maintaining homeostasis<\/li>\r\n \t
  • Explain the role of amino acid-derived hormones in maintaining homeostasis<\/li>\r\n \t
  • Explain the role of peptide hormones in maintaining homeostasis<\/li>\r\n \t
  • Explain how hormone production is regulated<\/li>\r\n<\/ul>\r\n<\/div>\r\n

    Lipid-Derived Hormones<\/h2>\r\nMaintaining homeostasis within the body requires the coordination of many different systems and organs. Communication between neighboring cells, and between cells and tissues in distant parts of the body, occurs through the release of chemicals called hormones. Hormones are released into body fluids (usually blood) that carry these chemicals to their target cells. At the target cells, which are cells that have a receptor for a signal or ligand from a signal cell, the hormones elicit a response. The cells, tissues, and organs that secrete hormones make up the endocrine system. Examples of glands of the endocrine system include the adrenal glands, which produce hormones such as epinephrine and norepinephrine that regulate responses to stress, and the thyroid gland, which produces thyroid hormones that regulate metabolic rates.\r\n\r\nMost lipid hormones<\/b> are derived from cholesterol and thus are structurally similar to it, as illustrated in Figure\u00a01. The primary class of lipid hormones in humans is the steroid hormones. Chemically, these hormones are usually ketones or alcohols; their chemical names will end in \u201c-ol\u201d for alcohols or \u201c-one\u201d for ketones. Examples of steroid hormones include estradiol, which is an estrogen<\/b>, or female sex hormone, and testosterone, which is an androgen, or male sex hormone. These two hormones are released by the female and male reproductive organs, respectively. Other steroid hormones include aldosterone and cortisol, which are released by the adrenal glands along with some other types of androgens. Steroid hormones are insoluble in water, and they are transported by transport proteins in blood. As a result, they remain in circulation longer than peptide hormones. For example, cortisol has a half-life of 60 to 90 minutes, while epinephrine, an amino acid derived-hormone, has a half-life of approximately one minute.\r\n\r\n[caption id=\"attachment_4342\" align=\"aligncenter\" width=\"1153\"]\"Part Figure\u00a01.\u00a0The structures shown here represent (a) cholesterol, plus the steroid hormones (b) testosterone and (c) estradiol.[\/caption]\r\n

    Amino Acid-Derived Hormones<\/h2>\r\nThe amino acid-derived hormones<\/b> are relatively small molecules that are derived from the amino acids tyrosine and tryptophan, shown in Figure\u00a02. If a hormone is amino acid-derived, its chemical name will end in -ine<\/em>. Examples of amino acid-derived hormones include epinephrine and norepinephrine, which are synthesized in the medulla of the adrenal glands, and thyroxine, which is produced by the thyroid gland. The pineal gland in the brain makes and secretes melatonin which regulates sleep cycles.\r\n\r\n[caption id=\"attachment_4346\" align=\"aligncenter\" width=\"1422\"]\"Part Figure\u00a02.\u00a0(a) The hormone epinephrine, which triggers the fight-or-flight response, is derived from the amino acid tyrosine. (b) The hormone melatonin, which regulates circadian rhythms, is derived from the amino acid tryptophan.[\/caption]\r\n

    Peptide Hormones<\/h2>\r\nThe structure of peptide hormones<\/b> is that of a polypeptide chain (chain of amino acids). The peptide hormones include molecules that are short polypeptide chains, such as antidiuretic hormone and oxytocin produced in the brain and released into the blood in the posterior pituitary gland. This class also includes small proteins, like growth hormones produced by the pituitary, and large glycoproteins such as follicle-stimulating hormone produced by the pituitary. Figure\u00a03\u00a0illustrates these peptide hormones.\r\n\r\n[caption id=\"attachment_2729\" align=\"aligncenter\" width=\"1024\"]\"Oxytocin, Figure\u00a03.\u00a0The structures of peptide hormones (a) oxytocin, (b) growth hormone, and (c) follicle-stimulating hormone are shown. These peptide hormones are much larger than those derived from cholesterol or amino acids.[\/caption]\r\n\r\nSecreted peptides like insulin are stored within vesicles in the cells that synthesize them. They are then released in response to stimuli such as high blood glucose levels in the case of insulin. Amino acid-derived and polypeptide hormones are water-soluble and insoluble in lipids. These hormones cannot pass through plasma membranes of cells; therefore, their receptors are found on the surface of the target cells.\r\n

    Hormone Regulation<\/h2>\r\nHormone production and release are primarily controlled by negative feedback. In negative feedback systems, a stimulus elicits the release of a substance; once the substance reaches a certain level, it sends a signal that stops further release of the substance.\u00a0In this way, the concentration of hormones in blood is maintained within a narrow range.\u00a0For example, the amount of glucose in the blood controls the secretion of insulin and glucagons via negative feedback.\r\n\r\nDuring hormone regulation, hormones are released, either directly by an endocrine gland or indirectly through the action of the hypothalamus of the brain, which stimulates other endocrine glands to release hormones in order\u00a0to maintain homeostasis. The hormones activate target cells, which initiate physiological changes that adjust the body conditions. When normal conditions have been recovered, the corrective action - the production of hormones - is discontinued. Thus, in negative feedback, when the original (abnormal) condition has been repaired, or negated, corrective actions decrease or discontinue.\r\n\r\nIn another example of hormone regulation, the anterior pituitary signals the thyroid to release thyroid hormones. Increasing levels of these hormones in the blood then give feedback to the hypothalamus and anterior pituitary to inhibit further signaling to the thyroid gland, as illustrated in Figure\u00a04.\r\n\r\n[caption id=\"attachment_2746\" align=\"aligncenter\" width=\"500\"]\"The Figure\u00a04.\u00a0The anterior pituitary stimulates the thyroid gland to release thyroid hormones T3<\/sub> and T4<\/sub>. Increasing levels of these hormones in the blood results in feedback to the hypothalamus and anterior pituitary to inhibit further signaling to the thyroid gland. (credit: modification of work by Mikael H\u00e4ggstr\u00f6m)[\/caption]\r\n

    Stimuli<\/h2>\r\nThere are three mechanisms by which endocrine glands are stimulated to synthesize and release hormones: humoral stimuli, hormonal stimuli, and neural stimuli.\r\n

    Humoral Stimuli<\/h3>\r\nThe term \"humoral\" is derived from the term \"humor,\" which refers to bodily fluids such as blood. A humoral stimuli<\/strong>\u00a0refers to the control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood. For example, a rise in blood glucose levels triggers the pancreatic release of insulin. Insulin causes blood glucose levels to drop, which signals the pancreas to stop producing insulin in a negative feedback loop.\r\n

    Hormonal Stimuli<\/h3>\r\nHormonal stimuli<\/strong> refers to the release of a hormone in response to another hormone. A number of endocrine glands release hormones when stimulated by hormones released by other endocrine glands. For example, the hypothalamus produces hormones that stimulate the anterior portion of the pituitary gland. The anterior pituitary in turn releases hormones that regulate hormone production by other endocrine glands. The anterior pituitary releases the thyroid-stimulating hormone, which then stimulates the thyroid gland to produce the hormones T3<\/sub> and T4<\/sub>. As blood concentrations of T3<\/sub> and T4<\/sub> rise, they inhibit both the pituitary and the hypothalamus in a negative feedback loop.\r\n

    Neural Stimuli<\/h3>\r\nIn some cases, the nervous system directly stimulates endocrine glands to release hormones, which is referred to as neural stimuli<\/strong>. Recall that in a short-term stress response, the hormones epinephrine and norepinephrine are important for providing the bursts of energy required for the body to respond. Here, neuronal signaling from the sympathetic nervous system directly stimulates the adrenal medulla to release the hormones epinephrine and norepinephrine in response to stress.\r\n
    \r\n

    Practice Question<\/h3>\r\nHyperthyroidism is a condition in which the thyroid gland is overactive. Hypothyroidism is a condition in which the thyroid gland is underactive. Which of the conditions are the following two patients most likely to have?\r\n
      \r\n \t
    • Patient A has symptoms including weight gain, cold sensitivity, low heart rate and fatigue.<\/li>\r\n \t
    • Patient B has symptoms including weight loss, profuse sweating, increased heart rate and difficulty sleeping.<\/li>\r\n<\/ul>\r\n[reveal-answer q=\"71349\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"71349\"]Patient A has symptoms associated with decreased metabolism, and may be suffering from hypothyroidism. Patient B has symptoms associated with increased metabolism, and may be suffering from hyperthyroidism.[\/hidden-answer]\r\n\r\n<\/div>\r\n

      Check Your Understanding<\/strong><\/h2>\r\nAnswer the question(s) below to see how well you understand the topics covered in the previous section. This short quiz does\u00a0not<\/strong>\u00a0count toward your grade in the class, and you can retake it an unlimited number of times.\r\n\r\nUse this quiz to check your understanding and decide whether to (1) study the previous section further or (2) move on to the next section.\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/5005","rendered":"

      Identify different types of hormones and explain the regulation of hormone production<\/h2>\n

      Although there are many different hormones in the human body, they can be divided into three classes based on their chemical structure: lipid-derived, amino acid-derived, and peptide (peptide and proteins) hormones. One of the key distinguishing features of lipid-derived hormones is that they can diffuse across plasma membranes whereas the amino acid-derived and peptide hormones cannot.<\/p>\n

      \n

      Learning Objectives<\/h3>\n
        \n
      • Explain the role of lipid-derived hormones in maintaining homeostasis<\/li>\n
      • Explain the role of amino acid-derived hormones in maintaining homeostasis<\/li>\n
      • Explain the role of peptide hormones in maintaining homeostasis<\/li>\n
      • Explain how hormone production is regulated<\/li>\n<\/ul>\n<\/div>\n

        Lipid-Derived Hormones<\/h2>\n

        Maintaining homeostasis within the body requires the coordination of many different systems and organs. Communication between neighboring cells, and between cells and tissues in distant parts of the body, occurs through the release of chemicals called hormones. Hormones are released into body fluids (usually blood) that carry these chemicals to their target cells. At the target cells, which are cells that have a receptor for a signal or ligand from a signal cell, the hormones elicit a response. The cells, tissues, and organs that secrete hormones make up the endocrine system. Examples of glands of the endocrine system include the adrenal glands, which produce hormones such as epinephrine and norepinephrine that regulate responses to stress, and the thyroid gland, which produces thyroid hormones that regulate metabolic rates.<\/p>\n

        Most lipid hormones<\/b> are derived from cholesterol and thus are structurally similar to it, as illustrated in Figure\u00a01. The primary class of lipid hormones in humans is the steroid hormones. Chemically, these hormones are usually ketones or alcohols; their chemical names will end in \u201c-ol\u201d for alcohols or \u201c-one\u201d for ketones. Examples of steroid hormones include estradiol, which is an estrogen<\/b>, or female sex hormone, and testosterone, which is an androgen, or male sex hormone. These two hormones are released by the female and male reproductive organs, respectively. Other steroid hormones include aldosterone and cortisol, which are released by the adrenal glands along with some other types of androgens. Steroid hormones are insoluble in water, and they are transported by transport proteins in blood. As a result, they remain in circulation longer than peptide hormones. For example, cortisol has a half-life of 60 to 90 minutes, while epinephrine, an amino acid derived-hormone, has a half-life of approximately one minute.<\/p>\n

        \"Part<\/p>\n

        Figure\u00a01.\u00a0The structures shown here represent (a) cholesterol, plus the steroid hormones (b) testosterone and (c) estradiol.<\/p>\n<\/div>\n

        Amino Acid-Derived Hormones<\/h2>\n

        The amino acid-derived hormones<\/b> are relatively small molecules that are derived from the amino acids tyrosine and tryptophan, shown in Figure\u00a02. If a hormone is amino acid-derived, its chemical name will end in –ine<\/em>. Examples of amino acid-derived hormones include epinephrine and norepinephrine, which are synthesized in the medulla of the adrenal glands, and thyroxine, which is produced by the thyroid gland. The pineal gland in the brain makes and secretes melatonin which regulates sleep cycles.<\/p>\n

        \"Part<\/p>\n

        Figure\u00a02.\u00a0(a) The hormone epinephrine, which triggers the fight-or-flight response, is derived from the amino acid tyrosine. (b) The hormone melatonin, which regulates circadian rhythms, is derived from the amino acid tryptophan.<\/p>\n<\/div>\n

        Peptide Hormones<\/h2>\n

        The structure of peptide hormones<\/b> is that of a polypeptide chain (chain of amino acids). The peptide hormones include molecules that are short polypeptide chains, such as antidiuretic hormone and oxytocin produced in the brain and released into the blood in the posterior pituitary gland. This class also includes small proteins, like growth hormones produced by the pituitary, and large glycoproteins such as follicle-stimulating hormone produced by the pituitary. Figure\u00a03\u00a0illustrates these peptide hormones.<\/p>\n

        \"Oxytocin,<\/p>\n

        Figure\u00a03.\u00a0The structures of peptide hormones (a) oxytocin, (b) growth hormone, and (c) follicle-stimulating hormone are shown. These peptide hormones are much larger than those derived from cholesterol or amino acids.<\/p>\n<\/div>\n

        Secreted peptides like insulin are stored within vesicles in the cells that synthesize them. They are then released in response to stimuli such as high blood glucose levels in the case of insulin. Amino acid-derived and polypeptide hormones are water-soluble and insoluble in lipids. These hormones cannot pass through plasma membranes of cells; therefore, their receptors are found on the surface of the target cells.<\/p>\n

        Hormone Regulation<\/h2>\n

        Hormone production and release are primarily controlled by negative feedback. In negative feedback systems, a stimulus elicits the release of a substance; once the substance reaches a certain level, it sends a signal that stops further release of the substance.\u00a0In this way, the concentration of hormones in blood is maintained within a narrow range.\u00a0For example, the amount of glucose in the blood controls the secretion of insulin and glucagons via negative feedback.<\/p>\n

        During hormone regulation, hormones are released, either directly by an endocrine gland or indirectly through the action of the hypothalamus of the brain, which stimulates other endocrine glands to release hormones in order\u00a0to maintain homeostasis. The hormones activate target cells, which initiate physiological changes that adjust the body conditions. When normal conditions have been recovered, the corrective action – the production of hormones – is discontinued. Thus, in negative feedback, when the original (abnormal) condition has been repaired, or negated, corrective actions decrease or discontinue.<\/p>\n

        In another example of hormone regulation, the anterior pituitary signals the thyroid to release thyroid hormones. Increasing levels of these hormones in the blood then give feedback to the hypothalamus and anterior pituitary to inhibit further signaling to the thyroid gland, as illustrated in Figure\u00a04.<\/p>\n

        \"The<\/p>\n

        Figure\u00a04.\u00a0The anterior pituitary stimulates the thyroid gland to release thyroid hormones T3<\/sub> and T4<\/sub>. Increasing levels of these hormones in the blood results in feedback to the hypothalamus and anterior pituitary to inhibit further signaling to the thyroid gland. (credit: modification of work by Mikael H\u00e4ggstr\u00f6m)<\/p>\n<\/div>\n

        Stimuli<\/h2>\n

        There are three mechanisms by which endocrine glands are stimulated to synthesize and release hormones: humoral stimuli, hormonal stimuli, and neural stimuli.<\/p>\n

        Humoral Stimuli<\/h3>\n

        The term “humoral” is derived from the term “humor,” which refers to bodily fluids such as blood. A humoral stimuli<\/strong>\u00a0refers to the control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood. For example, a rise in blood glucose levels triggers the pancreatic release of insulin. Insulin causes blood glucose levels to drop, which signals the pancreas to stop producing insulin in a negative feedback loop.<\/p>\n

        Hormonal Stimuli<\/h3>\n

        Hormonal stimuli<\/strong> refers to the release of a hormone in response to another hormone. A number of endocrine glands release hormones when stimulated by hormones released by other endocrine glands. For example, the hypothalamus produces hormones that stimulate the anterior portion of the pituitary gland. The anterior pituitary in turn releases hormones that regulate hormone production by other endocrine glands. The anterior pituitary releases the thyroid-stimulating hormone, which then stimulates the thyroid gland to produce the hormones T3<\/sub> and T4<\/sub>. As blood concentrations of T3<\/sub> and T4<\/sub> rise, they inhibit both the pituitary and the hypothalamus in a negative feedback loop.<\/p>\n

        Neural Stimuli<\/h3>\n

        In some cases, the nervous system directly stimulates endocrine glands to release hormones, which is referred to as neural stimuli<\/strong>. Recall that in a short-term stress response, the hormones epinephrine and norepinephrine are important for providing the bursts of energy required for the body to respond. Here, neuronal signaling from the sympathetic nervous system directly stimulates the adrenal medulla to release the hormones epinephrine and norepinephrine in response to stress.<\/p>\n

        \n

        Practice Question<\/h3>\n

        Hyperthyroidism is a condition in which the thyroid gland is overactive. Hypothyroidism is a condition in which the thyroid gland is underactive. Which of the conditions are the following two patients most likely to have?<\/p>\n

          \n
        • Patient A has symptoms including weight gain, cold sensitivity, low heart rate and fatigue.<\/li>\n
        • Patient B has symptoms including weight loss, profuse sweating, increased heart rate and difficulty sleeping.<\/li>\n<\/ul>\n
          Show Answer<\/span><\/p>\n
          Patient A has symptoms associated with decreased metabolism, and may be suffering from hypothyroidism. Patient B has symptoms associated with increased metabolism, and may be suffering from hyperthyroidism.<\/div>\n<\/div>\n<\/div>\n

          Check Your Understanding<\/strong><\/h2>\n

          Answer the question(s) below to see how well you understand the topics covered in the previous section. This short quiz does\u00a0not<\/strong>\u00a0count toward your grade in the class, and you can retake it an unlimited number of times.<\/p>\n

          Use this quiz to check your understanding and decide whether to (1) study the previous section further or (2) move on to the next section.<\/p>\n

          \t