A few basic definitions are in order to start off. Free T4 and T3 are the actual, available hormones the body can use. T4 is deiodinated to T3, which is used by the body, in the pituitary gland, liver, and kidneys. This process is important to understand, since a condition called euthyroid sick syndrome, or nonthyroidal illness, may affect the deiodination pathway. In these cases, proper diagnosis and treatment of the real underlying disease process can also lead to a resolution of the secondary thyroid problem.
Hypothyroidism affects many systems in the body.
Less common symptoms, which may be encountered, include neuromuscular changes, cardiac problems, and behavioral changes. Hypothyroidism very commonly produces some typical skin and coat changes. One of the most important things to remember is that low thyroid levels do NOT lead to itchy skin. The hair loss is usually symmetrical, and often most noticeable over the rump to start. The hair may lighten in color.