Iodine excretion

The counting regime for patients with intact thyroid glands was begun within a week of the initial administration of with repeat counts being performed at approximately 7-day intervals, however, the regime for athyreotic patients had to commence as quickly as possible to measure the rapidly excreted iodine. Repeat counts were daily (where possible) for the first 3 days, and the last counts were at a weekly interval. 

Note The tabie shows associations between various ways to measure iodine intake and thyroid voiume in the same popuiation (Rasmussen etal., 2002). Thyroid voiume is inciuded as a dependent variabie and a measure of iodine intake as an independent variabie in a muitipie iinear regression modei. Each measure of iodine intake is inciuded in a separate modei. Other dependent variabies in the modeis inciude city, age and gender group, smoking (daiiy smoker or not daiiy smoker), drinking (>8 drinks/week or <8 drinks per week), and thyroid disease in the famiiy. P < 0.001 for aii these variabies. Subjects being treated for thyroid disease n = 77) were not inciuded in the anaiyses. Estimated 24-h iodine excretion iodine-to-creatinine ratio muitipiied by the expected daiiy creatinine excretion for the given individuai. 

Year of investigation Age (years) Sex iodine excretion iodine excretion iodine excretion iodine intake Method Reference... 

Iodine excretion Iodine excretion Iodine intake ... 

Strong iodide solutions act by decreasing the vascularity of the thyroid gland by rapidly inhibiting the release of the thyroid hormones. Radioactive iodine is distributed within the cellular fluid and excreted. The radioactive isotope accumulates in the cells of the tiiyroid gland, where destruction of tiiyroid cells occurs without damaging other cells throughout the body. 

X-ray contrast agents, as triiodinated benzoates, permit visualization of the details of the internal structure of organs that would otherwise not be apparent. Given that iodinated X-ray contrast agents are very stable and chemically inert, they are excreted untransformed by humans and are not degraded in their subsequent pass through WWTPs. 

Ohira S, Kirk AB, Dyke JV, DasguptaPK (2008) Creatinine adjustment of spot urine samples and 24 h excretion of iodine, selenium, perchlorate, and thiocyanate. Environ Sci Technol 42 9419-9423... 

Dasgupta PK, Kirk AB, Dyke JV, Ohira S (2008) Intake of iodine and perchlorate and excretion in human milk. Environ Sci Technol 42 8115-8121... 

Most contrast agents elicit nephrotoxicity because they are primarily excreted by the kidneys. However, when administered in small doses, they constitute a rich source of GFR markers. The two major classes of contrast agents that are finding clinical utility as GFR markers are iodinated aromatic compounds and metal complexes. lodinated aromatics such as iohexol and iothalamate (Fig. 13) are commonly used as contrast agents for computed tomography (GT). They also have pharmacokinetics similar to inulin and hence are useful indicators of renal status [215]. The iodinated molecules used for GFR measurements consist of a triiodo-benzene core and hydrophilic groups to enhance solubility in aqueous medium. 

As the human body is able to store many minerals, deviations from the daily ration are balanced out over a given period of time. Minerals stored in the body include water, which is distributed throughout the whole body calcium, stored in the form of apatite in the bones (see p. 340) iodine, stored as thyroglobulin in the thyroid and iron, stored in the form of ferritin and hemosiderin in the bone marrow, spleen, and liver (see p. 286). The storage site for many trace elements is the liver. In many cases, the metabolism of minerals is regulated by hormones—for example, the uptake and excretion of H2O, Na, ... 

Countries affected by iodine deficiency require to develop national programmes to assess the extent and severity of the problem. Once an IDD control programme is initiated monitoring and evaluation are required. There are three major components needed to meet this goal, namely determination of thyroid size and goitre prevalence, the determination of urinary iodine excretion, and the measurement of thyroid function, including serum TSH levels. 

Urinary Iodine Excretion (UIE) provides the best single measurement of iodine intake of the population and Should be used for initial and follow up assessment. For epidemiological studies, population and not individual levels are is required. To achieve this 40 casual samples from a particular group can be collected (may be collected from schoolchildren at the same time as the goiter is assessed). The values are expressed as a median. Median UIE in the population below 100 pg/1 indicate iodine deficiency. Thus median UIE 10 pg/1 means no deficiency, 50-99 pg/1 indicates mild, 20 9 pg/1 moderate, and <20 pg/1 severe IDD. 

Mechanism of Action A thioimidazole derivative that inhibits synthesis of thyroid hormone by interfering with the incorporation of iodine into tyrosyl residues. Thera-peuticEffect Effectively treats hyperthyroidism by decreasingthyroid hormone levels. Pharmacohinetics Rapid absorption following PO administration. Protein binding Not significant. Widely distributed throughout the body. Metabolized in liver. Excreted in urine. Half-life 5-6 hr. 

Metabolically, radionuclides are handled in the same way as stable elements of the same atomic numher. Thus radioactive iodine simulates stable iodine, being concentrated in the thyroid gland so predictably that its rate of uptake provides an accurate measure of thyroid function. The metabolism of other radionuclides also is sufficiently characteristic so that their patterns of uptake, distribution, translocation, and excretion are similarly predictable. 

Iodide, ingested from food, water, or medication, is rapidly absorbed and enters an extracellular fluid pool. The thyroid gland removes about 75 meg a day from this pool for hormone synthesis, and the balance is excreted in the urine. If iodide intake is increased, the fractional iodine uptake by the thyroid is diminished. 

Hollowell G, Norman W, Staehling W, et al. 1998. Iodine nutrition in the United States. Trends and public health implications Iodine excretion data from national health and nutrition examination surveys I and III (1971-1974 and 1988-1994). J Clin Endocrinol Metab 83(10) 3401-3408. 

Dydek GJ, Blue PW. Human breast milk excretion of iodine-131 following diagnostic and therapeutic administration to a lactating patient with Graves disease. J Nucl Med 1988 29(3) 407-10. 

The use of povidone-iodine for the treatment of burns, for peritoneal lavage in the treatment of purulent peritonitis, or as a rinsing solution for body cavities can increase serum iodine concentrations associated with increased urinary excretion of iodine. In people with burns the extent of iodine absorption depends on the extent of the burned body surface. It is not uncommon for serum iodine concentrations to rise to more than 1000 pg/ml. If renal function is intact, iodine elimination in the urine can be adequate. The serum iodine concentration returns to normal about 1 week after the last application. 

In 99 of 9320 newborns TSH concentrations were above the reference range (20 mU/ml) on the fifth day of life, but between the 10th and 21st day all these infants had normal TSH concentrations and normal thyroid function (38). In 76 of the newborns with hyperthyrotropinemia, urinary iodine excretion was significantly raised (above 16 pg/ml). Most of them were born in obstetric departments where iodophores were routinely used for disinfection during labor. 

---