Iodine in biology
The U.S. Food and Nutrition Board and Institute of Medicine recommended daily allowance of iodine ranges from 150 micrograms per day for adult humans to 290 micrograms per day for lactating mothers. However, the thyroid gland needs no more than 70 micrograms per day to synthesize the requisite daily amounts of T4 and T3. The higher recommended daily allowance levels of iodine seem necessary for optimal function of a number of other body systems, including lactating breasts, gastric mucosa, salivary glands, oral mucosa, arterial walls, thymus, epidermis, choroid plexus and cerebrospinal fluid, among others.
Indocyanine green
Because the preparation contains sodium iodide, a test must be carried out for iodine intolerance. Because around 5% of iodide is added, the iodine content of a 25 mg ampoule is 0.93 mg. In comparison, preparations for a bone marrow CT (140 ml) contain 300 mg/ml and for a corona angiography (200 ml) 350 mg/ml of iodine. ICG has the ability to bind 98% to plasma proteins – 80% to globulins and 20% to alpha-lipoprotein and albumin – and thus, in comparison with fluorescein as a marker, has a lower leakage (slower emergence of dye from the vessels, extravasally). Because of the plasma protein binding, ICG stays for up to 20–30 minutes in the vessels (intravasally). When the eye is examined, it thus stays for a long time in tissues with a higher blood flow, such as the choroid and the blood vessels of the retina.