Medical Dictionary Definitions A-Z List
Medical Dictionary Definitions A - Z - «I»:
Inverted repeat: A sequence of nucleotides in the DNA that is identical to another except that it has been reversed (inverted) in direction. See also: Repeat....
Invest: In medicine, this has nothing to do with the stock
market. It means to envelop, cover, or embed. ...
Involuntary: Done other than in accordance with the conscious will of the individual. The opposite of voluntary.
The terms "voluntary" and "involuntary" apply to the human nervous system and its control over muscles. The nervous system is divided into two parts -- somatic and autonomic. The somatic ...
Involuntary smoking: The involuntary inhaling of environmental tobacco smoke (ETS) by someone who is not smoking. See: ETS....
Involute: 1. Literally, to turn inward or roll inward.
2. To decrease in size after an enlargement. The uterus involutes after pregnancy. The thymus involutes after adolescence.
3. To undergo a retrograde change. After treatment, a tumor may involute.
4. To shrink physically and emotionally with...
Involution: 1. Literally, a turning inward or rolling inward.
2. A decrease in size, usually after an increase. The uterus involutes after pregnancy.
3. A retrograde change. After treatment, a tumor may involute.
4. With advancing age, there may be physical and emotional involution. This process h...
Iodide: The chemical form to which iodine in the diet is reduced before it is absorbed through the intestinal wall into the bloodstream and carried through the blood to the thyroid gland....
Iodide goiter: See Iodine excess....
Iodine: An essential element in the diet used by the thyroid gland to make thyroid hormones.
The two most important thyroid hormones are
thyroxine (T4) and triiodothyronine (T3). Thyroxine (T4) has four iodine molecules
attached to its structure, while triiodothyronine (T3) has three iodine molecul...
Iodine deficiency: Iodine is a natural requirement of
our diets. Iodine deficiency can lead to inadequate production of thyroid hormone from the
thyroid gland (hypothyroidism). For example, in some parts of Zaire, Ecuador, India, and
Chile, remote, mountainous areas, such as in the Alps (in the past...
Iodine excess: Just as too little iodine can cause
thyroid disease, so may prolonged intake of too much iodine also lead to the development
of goiter (swelling of the thyroid gland) and hypothyroidism (abnormally low thyroid
activity). Certain foods and medications contain large amounts of iodine. E...
Iodine, radioactive: An isotope of the chemical
element iodine that is radioactive. Radioactive iodine is used in diagnostic
tests as well as in radiotherapy of an hyperactive thyroid gland (hyperthyroidism), most often due to Graves disease.
For hyperthyroidism, Radioactive iodine is administe...
Ion channel: A protein that acts as a pore in a cell membrane and permits the selective passage of ions (such as potassium ions, sodium ions, and calcium ions), by means of which electrical current passes in and out of the cell. Ion channels also serve many other critically important functions inclu...
Iontophoresis: A transdermal delivery system in which a substance bearing a charge is propelled through the skin by a low electrical current. This method can be used to drive a drug across the skin barrier, as is done with pilocarpine to stimulate sweating in the sweat chloride test for cystic fibro...
IOP (intraocular pressure)
IOP (intraocular pressure): The pressure created by the continual renewal of fluids within the eye. The normal IOP varies among individuals. The intraocular pressure is increased in glaucoma.
In acute angle-closure glaucoma, the intraocular pressure rises because the canal which normally drains the ...