Viagra (sildenafil) and other similar products (Levitra and Cialis) are in the class of drugs known as phosphodiesterase type-5 (PDE5) inhibitors. When sildenafil failed to qualify as a product in the antihypertensive market, penile erection, one of its side effects, was used as an opportunity to market it as something that was never before offered, for a condition never medicinally treated before. Suddenly, impotence became a dysfunction called erectile dysfunction and dysfunction meant a medical abnormality that warranted treatment.
Nitric oxide (NO) widens blood vessels, thereby increasing circulation, and also inhibits the breakdown of a cyclic guanosine monophosphate (CGM), which controls nitric oxide’s role in vasodilation, by phosphodiesterase. By inhibiting the breakdown of the controlling CGM phosphate, the nitric oxide can continue to vasodilate.
Viagra, a PDE5 inhibitor, took the market by storm when it was first made available. Beca ...
Abnormalities of the thyroid fall into two categories:
Hypothyroidism—This refers to under-functioning of the thyroid.
Hyperthyroidism—This refers to over-functioning of the thyroid.
Some other definitions
Goiter: This is the swelling of thyroid tissue and can occur because of hypothyroidism.
Thyrotoxicity: This is symptomatic hyperthyroidism with hyperactive metabolism.
Thyroxine is the thyroid hormone T4 and is made in the thyroid.
Tri-iodothyronine is the thyroid hormone T3 and is made in the thyroid.
Thyroid-stimulating hormone is also known as TSH and is made in the pituitary gland of the brain when stimulated by hypothalamic TRH.
TRH is the thyrotropin-releasing hormone and is made in the hypothalamus of the brain.
A tale of two hormones
Tri-iodothyronine (T3) is the active hormone of the body that controls the rate of metabolism, growth, and body temperature. T3 is broken down from thyroxine (T4), another thyroid ...