Thyrotoxicosis can be easily discovered with elevated free T4 or T3 levels and a TSH level that is lower than normal (usually less than 0.2). See Chapter 2 for more details on lab testing for TSH and free T4 and T3.
The challenge for diagnosing either hyperthyroidism and/or thyrotoxicosis is similar for hypothyroidism: the symptoms can overlap with stress, anxiety, panic disorder, low blood sugar, and cardiovascular diseases. For women, PMS and perimenopause can mask, or be mistaken for, thyrotoxicosis; miscarriage or infertility can also result from thyrotoxicosis.
In my (Sara's) case, I suffered from thyrotoxic symptoms for more than four years, in the belief that I had low blood sugar and panic disorder. Having been on a TSH-suppression dosage of thyroid hormone most of my adult life, as I aged, I became less tolerant but didn't realize it. A few years later, after Ken and I were married (and he witnessed a few of these episodes), he also noticed one day that my heart was racing. Ken suggested my panic attacks and "hypoglycemic" reactions might be caused by thyrotoxicosis, which, as discussed previously, makes people oversensitive to their own adrenaline. Of course, this would be the logical result of being on a high dosage of T4 all of those years. After starting a beta-blocker, which blocks the adrenaline rush symptoms of thyrotoxicosis, my panic attacks and "hypoglycemia" vanished. Anyone under the belief that he or she is suffering from panic disorder or low blood sugar should request a thyroid screening to rule out thyrotoxicosis.
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