Hypothyroidism or low thyroid hormone is a common condition in North America, particularly in Canada and the upper U.S. states where levels of sunlight are low for much of the year, and soil mineral depletion is common. Low thyroid function affects approximately 20-25 percent of the female population and about 10 percent of males. An additional 30 percent of persons over the age of 35 may also have sub-clinical or mild hypothyroidism whereby their thyroid stimulating hormone (TSH) is within normal range, but they have many of the symptoms of low thyroid.
Hypothyroid symptoms insclude fatigue, morning headaches that wear off during the day, increasein weight, sensitivity to cold, dry brittle hair, hair that falls out easily, dry, scaly or itching skin, poor memory, low axillary temperature, muscle cramps at rest, reduced immune function, constipation, loss of outside portion of eyebrows, depression, premature grey hair, red hair and more.........TSH alone is not an accurate test as you may be considered "normal" but if 3 or more of these symptoms match you, you may be subclinical and additional tests should be run.
Free T3 and Free T4 both need to be looked at in a lab. Labs are created using sick people, so you want to be at the upper end of the range because we're looking for optimal, not just normal! For example, if the lab ranges for Free T3 is 2.0-4.0, the median is clearly 3.0 so a lab above 3.0 is a good place to start.