Examples of hormone in the following topics:
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- There are three classes of hormones: peptide hormones, lipid hormones, and monoamine hormones.
- Some peptide hormones contain carbohydrate side chains and are termed glyco-proteins, such as the follicle-stimulating hormone.
- All peptide hormones are hydrophilic and are therefore unable to cross the plasma membrane alone.
- Eicosanoids are also lipid hormones that are derived from fatty acids in the plasma membrane.
- Unlike other hormones, eicosanoids are not stored in the cell—they are synthesized as required.
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- As a result, hormonal signaling is elaborate and hard to dissect.
- The reaction of the target cells may then be recognized by the original hormone-producing cells, leading to a down-regulation in hormone production.
- Transport of the hormone to the target cells, tissues, or organs.
- Nuclear hormone receptors are activated by a lipid-soluble hormone such as estrogen, binding to them inside the cell.
- Lipid-soluble hormones can cross the plasma membrane.
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- During hormone replacement therapy the patient receives hormones either as a supplement or substitution to the natural hormone.
- Hormone replacement therapy refers to any form of hormone therapy wherein the patient, in the course of medical treatment, receives hormones, either to supplement a lack of naturally occurring hormones, or to substitute other hormones for naturally occurring hormones.
- Common forms of hormone replacement therapy include:
- This includes female-to-male and male-to-female hormone replacement therapy.
- Estrogens have been extensively used in hormone replacement therapies in women.
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- The production of thyroxine and triiodothyronine is regulated by thyroid-stimulating hormone (TSH) that is released from the anterior pituitary.
- TSH release, in turn, stimulates the hypothalamus to secrete thyrotropin-releasing hormone (TRH).
- Thyroid hormones also provide negative feedback to the hypothalamus and anterior pituitary gland.
- Thyroid hormones are produced from the thyroid under the influence of thyroid-stimulating hormone (TSH) from the anterior pituitary gland, which is itself under the control of thyroptropin-releasing hormone (TRH) secreted by the hypothalamus.
- Thyroid hormones provide negative feedback, inhibiting secretion of TRH and TSH when blood levels are high.
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- A hormone's half-life and duration of activity are limited and vary from hormone to hormone.
- The number of hormone molecules that are available is determined by the concentration of circulating hormones.
- A hormone's half-life and duration of activity are limited and vary from hormone to hormone.
- Follicle-stimulating hormone 2.
- Luteinizing hormone 4.
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- Hormonal control of spermatogenesis varies among species.
- They are capable of producing the hormones estradiol and inhibin.
- Follicle-stimulating hormone (FSH) is released by the anterior pituitary gland.
- Luteinizing hormone (LH) is released by the anterior pituitary gland.
- The hormone is released into the circulation when the sperm count is too high.
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- A hormone receptor is a molecule that binds to a specific hormone.
- Receptors for peptide hormones tend to be found on the plasma membrane of cells, whereas receptors for lipid-soluble hormones are usually found within the cytoplasm.
- The hormone activity within a target cell is dependent on the effective concentration of hormone-receptor complexes that are formed.
- Many hormones are composed of polypeptides—such as thyroid-stimulating hormones, follicle-stimulating hormones, luteinizing hormones, and insulin.
- Lipophilic hormones—such as steroid or thyroid hormones—are able to pass through the cell and nuclear membrane; therefore receptors for these hormones do not need to be, although they sometimes are, located in the cell membrane.
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- Hormones target a limited number of cells (based on the presence of a specific receptor) as they circulate in the bloodstream.
- In endocrinology, target cells can refer to the cells where hormones have an effect.
- Target cells are capable of responding to hormones because they display receptors to which the circulating hormone can bind.
- For example, after receptor stimulation the signaling target cell often sends feedback to the hormone-secreting tissue to down-regulate hormone expression.
- Finally, hormone–receptor affinity can be altered by the expression of associated inhibitory or co-activating factors.
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- Hormones synthesized by the endocrine glands are transported throughout the body by the bloodstream.
- For example, hormones secreted by the pancreas pass into the hepatic portal vein that transports them directly to the liver.
- Mainly produced in the liver, these transport proteins are hormone specific, such as the sex hormone binding globulin that binds with the sex hormones.
- When bound with a transport protein hormones are typically inactive, and their release is often triggered in regions of low hormone concentration or can be controlled by other factors.
- Describe the way in which hormones are transported in the endocrine system
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- The primary function of the thyroid is to produce the hormones triiodothyronine (T3), thyroxine (T4), and calcitonin.
- T4 is thought to be a pro-hormone to the more metabolically active T3.
- Calcitonin is another hormone released by the thyroid gland that is responsible for modulating blood calcium levels in conjunction with parathyroid hormone, which is released from the parathyroid.
- Only a very small fraction of the circulating hormone is free—T4 0.03% and T3 0.3%.
- Only the free fraction has hormonal activity.