LAURIUM - When people begin to have medical issues, problems with their thyroid levels are likely not the first thing to pop into their head.
Yet if someone has too much of the hormone - or not enough - it can have vast effects throughout the body, primarily having to do with metabolism.
"Thyroid controls the speed of metabolism inside cells," Dr. Steven Woodworth, an endocrinologist with Aspirus Keweenaw, said. "The more thyroid you have, the faster it burns calories. ... It's partly for climate control, as in a warm climate, the brain will turn down the cells' metabolism so you don't overheat."
As a result of that climate control, one of the main symptoms of hypothyroidism (too little thyroid) is feeling cold all the time, and a main symptom of hyperthyroidism (too much thyroid) is feeling hot all the time. However, there are other symptoms.
"The other fallout or other symptoms people would have if they're burning calories too fast would be unexpected weight loss," Woodworth said. "It also has effects on how fast the cells in the bowel work, as with too much thyroid people will often have diarrhea, and with too little thyroid they will have constipation.
"It also has effects on memory, as particularly too little thyroid tends to cause a sluggish memory."
In fact, the mystery of what causes Alzheimer's may have something to do with lower thyroid levels, he said.
"Chronic low thyroid might be a factor in chronic memory function," Woodworth said. "Nobody knows what causes Alzheimer's, but low thyroid might be a factor, maybe as much as 20 percent."
Thyroid problems tend to be more common in the Midwest, as there is not as much iodine in the soil as in other parts of the country. The thyroid hormone is made up of iodine and an amino acid, so if the body lacks iodine, it cannot make thyroid, according to Woodworth.
"That's why you see iodized salt," he said. "It was mandated to put (iodine) in the salt as a public health initiative many years ago."
Iodine and thyroid supplements are often the answer to treating thyroid problems, and babies are now screened at birth for thyroid problems, as it can hurt academic performance.
"It does affect children and can be a reason they're not performing well in school," Woodworth said. "There's now a mandate that all babies are checked at birth, as it leads to severe retardation if not caught early."
The common test for thyroid is the thyroid stimulating hormone test, which measures the pituitary hormone - the hormone that goes to the thyroid gland to tell it to make more thyroid. However, Woodworth warns against using the test as the lone measurement.
"The problem is that it's not really (measuring) a thyroid hormone," he said. "When there's not enough thyroid, the brain will turn up the TSH level, so by measuring TSH, you can tell that if they don't have enough TSH, there's too much thyroid.
"The problem therein, however, is that the test assumes brain function is normal," Woodworth continued. "A lot of people that have had head injuries or concussions, that may damage the area that controls the thyroid, therefore the TSH will not be a good indicator of TSH. What needs to be measured is the free thyroid-4 hormone, or FT4. That's the most accurate measurement we have currently for the amount of thyroid hormone traveling in the body."
Both tests should also be taken in context with the patient's history and symptoms, Woodworth said.
Hemorrhage at the time of childbirth can affect the pituitary gland, so women with difficult childbirths may have low thyroid as a result.
Snoring and sleep apnea can also both be made worse by low thyroid, and high cholesterol can be caused by a low thyroid.