This test takes about 4 minutes while the uptake % (i.e., percentage) is accumulated (calculated) by the machine software. A scan is also performed, wherein images (typically a center, left and right angle) are taken of the contrasted thyroid gland with a gamma camera; a radiologist will read and prepare a report indicating the uptake % and comments after examining the images. People with hyperthyroid will typically "take up" higher than normal levels of radioiodine. Normal ranges for RAI uptake are from 10 to 30%. In addition to testing the TSH levels, many doctors test for T3, Free T3, T4, and/or Free T4 for more detailed results. Free T4 is unbound to any protein in the blood. Adult limits for these hormones are: TSH (units): 0.45 – 4.50 uIU/mL; T4 Free/Direct (nanograms): 0.82 – 1.77 ng/dl; and T3 (nanograms): 71 – 180 ng/dl. Persons with hyperthyroidism can easily exhibit levels many times these upper limits for T4 and/or T3. See a complete table of normal range limits for thyroid function at the thyroid gland article. In hyperthyroidism CK-MB (Creatine kinase) is usually elevated. Subclinical
In overt primary hyperthyroidism, TSH levels are low and T4 and T3 levels are high. Subclinical hyperthyroidism is a milder form of hyperthyroidism characterized by low or undetectable serum TSH level, but with a normal serum free thyroxine level. Although the evidence for doing so is not definitive, treatment of elderly persons having subclinical hyperthyroidism could reduce the number of cases of atrial fibrillation.
In excess, it both overstimulates metabolism and disrupts the normal functioning of sympathetic nervous system, causing "speeding up" of various body systems and symptoms resembling an overdose of epinephrine (adrenaline). These include fast heartbeat and symptoms of palpitations, nervous system tremor such as of the hands and anxiety symptoms, digestive system hypermotility, unintended weight loss, and, in lipid panel blood tests, a lower and sometimes unusually low serum cholesterol.Major clinical signs of hyperthyroidism include weight loss (often accompanied by an increased appetite), anxiety, heat intolerance, hair loss (especially of the outer third of the eyebrows), muscle aches, weakness, fatigue, hyperactivity, irritability, high blood sugar, excessive urination, excessive thirst, delirium, tremor, pretibial myxedema (in Graves disease), emotional lability, and sweating. Panic attacks, inability to concentrate, and memory problems may also occur. Psychosis and paranoia, common during thyroid storm, are rare with milder hyperthyroidism. Many persons will experience complete remission of symptoms 1 to 2 months after a euthyroid state is obtained, with a marked reduction in anxiety, sense of exhaustion, irritability, and depression. Some individuals may have an increased rate of anxiety or persistence of affective and cognitive symptoms for several months to up to 10 years after a euthyroid state is established. In addition, those with hyperthyroidism may present with a variety of physical symptoms such as palpitations and abnormal heart rhythms (the notable ones being atrial fibrillation), shortness of breath (dyspnea), loss of libido, amenorrhea, nausea, vomiting, diarrhea, gynecomastia and feminization. Long term untreated hyperthyroidism can lead to osteoporosis.