Radioactive iodine uptake

Radioactive iodine uptake (RAIU) Red blood cell (RBC) count (blood) Less than 6% in 2 hours ... 

An elevated 24-hour radioactive iodine uptake (RAIU) indicates true hyperthyroidism the patient s thyroid gland is overproducing T4, T3, or both (normal RAIU 10% to 30%). Conversely, a low RAIU indicates that the excess thyroid hormone is not a consequence of thyroid gland hyperfunction but is likely caused by thyroiditis or hormone ingestion. 

RAIU = radioactive iodine uptake TSH = thyroid-stimulating hormone h"4 uptake method TT4 X RT3LI method ... 

Thyroid suppression therapy- 75 to 100 mcg/day for 7 days radioactive iodine uptake is determined before and after administration of the hormone. 

Physiologic Function Testing, An example of this application is the assay of thyroid hormone levels in (lie blood winch, in turn, can aid in the assessment of thyroid function. The radioactive iodine uptake test, which involves the administration of a dose of l31l (iodine-131) to the patient, is also a valuable procedure in assessing thyroid function. At present, the technique is best reserved for problem cases rather than used as a primary screening test. The main disadvantage of this test is the effect of the dietary intake of iodine, which reacts in various ways in different individuals. 

Associated with increased radioactive iodine uptake, except iodine induced. 

Associated with decreased radioactive iodine uptake. 

Elevated radioactive iodine uptake (RAID) by the thyroid gland... 

Ross DS. Syndromes of thyrotoxicosis with low radioactive iodine uptake. Endocrino Metab Clin North Am 1998 27 169-185. 

The percent uptake of a tracer dose of radioactive iodine (the radioactive iodine uptake, or RAIU) can provide important information about the pathogenesis of thyrotoxic states (see below). 

Physical examination revealed blood pressure 180/90 mm Hg, heart rate 110/min, minimal proptosis, and an enlarged thyroid gland. Laboratory tests showed elevated thyroxine, resin uptake, radioactive iodine uptake, and antimicrosomal antibodies. A diagnosis of hyperimmune hyperthyroidism (Graves disease) was made. 

Radioiodine plays an important role in the diagnosis and treatment of various thyroid disorders. Production methods for various iodine isotopes, namely, and are briefly described in this paper. The chemistry of iodine and radiation effects in aqueous solutions and isotopic exchange reactions are also reviewed. An understanding of the chemistry of iodine is essential in isotope production, and for developing the procedure to prepare the radioactive iodine labeled pharmaceuticals. In radiochemical analysis of iodine, most environmental and biological samples can be accurately analyzed by neutron activation at trace levels. The use of potassium iodide (KI) has become an important remedy to prevent the harmful effects of radioiodine exposure under nuclear accident conditions. The inhibitory effect of KI administration on thyroid radioactive iodine uptake is discussed. 

The use of K1 serves as an important remedy to protect from radioiodine exposure under nuclear accident conditions. In principle, under normal circumstances, excess iodine decreases sodium—iodide symporter (NIS) on the thyroid cell surface, thereby inhibiting further access for iodine into the thyroid. Excess iodide administration at the appropriate time decreases thyroid radioactive iodine uptake (RAIU) by increasing the amount of nonradioactive... 

Previously published reports have described both sub-clinical and overt thyroid dysfunction as a result of excess iodine ingestion. Moreover, iodine-induced hypothyroidism is not rare, at least in iodine-replete areas. The possible underlying mechanisms of this impairment consist of both the inhibition of thyroid function by excess iodine and the iodine-induced enhancement of thyroid autoimmunity. On the basis that an excess iodine intake may cause hypothyroidism, several study results support iodine restriction for the treatment of hypothyroidism. The success rate of dietary iodine restriction alone, without thyroid hormone replacement, is reported to be approximately 50-80% in patients with primary hypothyroidism due to Hashimotos thyroiditis and other causes. Relatively mild hypothyroidism, high radioactive iodine uptake and uptake, increased free plasma iodine and... 

RAIU Radioactive iodine uptake TPO Thyroid peroxidase... 

Favorable conditions to the success of dietary iodine restriction in treating hypothyroidism Relatively mild hypothyroidism High radioactive iodine uptake High 99"Tc uptake Increased free plasma iodine Increased free urinary iodine excretion Presence of goiter... 

As expected with iodine repletion, and decrease in thyroid iodine clearance, the 24 h radioactive iodine uptake decreased from a previously high level of 51% to 19.1% in 1999, as the mean urinary iodine increased from 90.8p,g/g creatinine to a median urinary iodine of 341.3 p.g/24h (Table 87.3). In the study conducted by us (Moorthy et ai, 2001), the mean 2h radioactive iodine uptake was 4.9 2.3% and mean 24h radioactive iodine uptake was 19.1 8.0%. Using the cut-off of the 3rd and 97th percentile as normal, this would give a normal range for 2h uptake of 2-8.6% and for 24h uptake of 6.4—35%, in the presence of the current higher ingestion of iodine in the country. 

Table 87.3 Radioactive iodine uptake and urinary iodine excretion...

Study (year) Urinary iodine excretion 24h Radioactive iodine uptake (%)... 

Notes. Decrease in the 24 h radioactive iodine uptake in Nationai Capitai Territory of Deihi with time after sait iodization. Vaiues are expressed as geometric mean (standard error). 

Yoshinari et al. (1983) Observational study Japan Normalization of thyroid function in patients with goitrous hypothyroidism and preserved thyroid radioactive iodine uptake after avoidance of foods rich in iodine... 

Tajiri et al. (1986) Observational study Japan Existence of a reversible type of hypothyroidism sensitive to iodine restriction and characterized by higher radioactive iodine uptake and relatively minor changes in lymphocytic thyroiditis histologically compared with the irreversible type... 

Okamura et al. (1994) Observational study Japan Reversible recovery of thyroid function after iodine restriction in patients with juvenile goitrous hypothyroidism and high thyroidal radioactive iodine uptake despite chronic lymphocytic thyroiditis... 

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