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What are hormones?
- A hormone is a substance that exerts a physiological control over other cells in the body. Hormones are secreted into the body by a gland and usually exert their effect at a distant location.
- Hormones are the primary message transmitters of' the endocrine system.
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Negative feedback
- The mechanism that controls the release hormones.
- thyroid-releasing factor stimulates the release of thyroid stimulating hormone that in turn causes the thyroid gland to release its hormone, thyroxine.
- When the level of thyroxine in the blood rises above normal, the secretion of thyroid releasing factor is inhibited.
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Thyroid
produces the hormones thyroxine (T4), triiodothyronine (T3) and several other thyroid hormones. T3 is about four times as potent as T4, but much shorter acting.
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Effects of Thyroid Hormones
- Increased metabolic rate: Increased protein synthesis, Increased enzyme activity, Increased activity of mitochondria
- Changes in metabolism of dietary substances: Increased bone growth, Increased carbohydrate metabolism, Increased fat metabolism
- Changes in body mechanisms:
- Decreased body weight
- Increased heart rate
- Increased force of contraction in the heart
- Increased blood volume
- Increased blood pressure
- Increased respiration
- Increased GI motility
- Increased gastric secretions
- Increased CNS activity, nervousness
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Hyperthyroid
- Causes: Tumors, Autoimmune diseases (Grave�s Disease)
- Symptoms: Nervousness, Diarrhea, Increased heart rate, Fatigue, but inability to sleep, Increased sweating, Weight loss, Intolerance to heat
- Treatment
- Destroy part of thyroid gland with radioactive iodine
- Surgical removal of part of thyroid gland
- Drugs: Propylthiouracil (PTU), Potassium iodide and iodine (Lugol�s Solution), Thyroid Storm
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Hypothyroid
- Causes: Gland destruction, Lack of iodine, Pituitary dysfunction, Surgical removal of gland
- Symptoms: Goiter, Extreme somnolence, Slow heart rate, Decreased cardiac output, Weight gain, Constipation, High cholesterol
- Treatment
- Thyroid USP - T3 & T4
- Levothyroxine Sodium - T4 (Synthroid, Levoxyl, Levothroid, Unothroid)
- Liothyronine Sodium - T3 (Cytomel)
- Liotrix - T3 & T4 (Euthroid, Thyrolar)
- Take thyroid replacement at the same time each day
- Do not change brands without checking with physician
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PTU
- Propylthiouracil
- Blocks the synthesis of T3 and T4 and the conversion of T4 to T3.
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Methiamazole
- Tapazole
- Palliative treatment of hyperthyroidism to return the hyperthyroid patient to a normal metabolic state before a thyroidectomy and to control thyrotoxic crisis.
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Thyroid storm
Life threatening medical emergency
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Adrenals
- The adrenal glands are located on top of the kidneys.
- They are composed of two parts, the medulla and the cortex.
- The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine in response to sympathetic stimulation.
- The cortex secretes corticosteroids, composed of glucocorticoids and mineralocorticoids.
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Cushing�s Disease
- Increased secretion of corticosteroids
- weight gain, excess growth of facial hair, CNS changes and high blood pressure.
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Addison�s Disease
- Decreased secretion of corticosteroids
- dehydration, hypotension and muscle weakness
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Glucocorticoids
include cortisol and cortisone
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Effects of Cortisol
- Stimulation of gluconeogenesis (breakdown of amino acids into glucose)
- Decrease cellular use of glucose
- Increased blood glucose
- Mobilization of fatty acids from adipose tissue
- Antiinflammatory effects (mechanism unknown)
- Increase in circulating white blood cells
- Methylprednisolone (Medrol, Solu-Medrol, Depo-Medrol)
- Prednisone (Deltasone)
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�steroid taper�
doses of glucocorticoids should be reduced gradually, not abruptly, in order to give the adrenal glands time to start normal production.
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Androgens
- Promotes development and maintenance of male physical characteristics.
- Also produced by the ovaries in females
- The most important male hormone is testosterone, which is produced by the testes.
- Replacement therapy (pituitary disorders, testicular failure, castration)
- Anabolic action
- Breast cancer
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Estrogens
- Develop uterine lining (endometrium) and mammary glands for pregnancy
- Cause development of secondary sex characteristics in the female
- Effects of Abnormally High Levels of Estrogen: Inhibits LH surge which prevents ovulation, Mechanism of action for oral contraceptives
- Conjugated Estrogens (Premarin)
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Progesterone
- secreted mainly in the second half of the ovarian cycle.
- During pregnancy, ten times the normal amount of progesterone is secreted by the placenta.
- Progesterone promotes changes in the uterus to prepare for implantation of the fetus.
- Medroxyprogesterone (Provera)
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How do oral contraceptives work?
- sufficient quantities of progestins and estrogens can inhibit the LH surges, thus inhibiting ovulation.
- used to prevent conception, to give enough of the hormones to prevent ovulation, but not enough to cause unwanted side effects.
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Selective Estrogen Receptor Modulators (SERM�s)
- SERM�s compete with estrogen for binding sites in target tissues such as the breast and uterus.
- Tamoxifen (Nolvadex): Useful in adjuvant therapy and treatment of breast cancer, Recently approved for preventative therapy in women at high risk for primary breast cancer
- Raloxifene (Evista): Produces estrogen-like effects on bone and lipid metabolism, Does not stimulate breast or uterine tissue, Approved for prevention of osteoporosis, Not useful for hot flashes
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Bisphosphonates
- used to treat Padget�s Disease and hypercalcemia.
- used to prevent and treat osteoperosis
- Bisphosphonates are not hormones.
- Take at least 30 minutes before the first food, drink or medication of the day
- Take with a full glass of water (at least 6 to 8 ounces)
- Avoid lying down for at least 30 minutes after drug administration
- Oral: Alendronate (Fosamax),Risedronate (Actonel), Ibandronate (Boniva)
- Injectable: Pamidronate (Aredia)
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Agents for osteoporosis
- Raloxifene (Evista)
- Alendronate (Fosamax)
- Risedronate (Actonel)
- Ibandronate (Boniva)
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