A TSH blood test is commonly ordered when thyroid problems are suspected.  Possible indications of thyroid problems may include weight loss, weight gain, feelings of extreme hot or cold, tiredness, rapid heart rate and irregular menstrual cycles.

The average range of TSH in the blood is from .45 to 5.0.

Low levels of TSH in the blood may indicate an underactive thyroid gland, commonly referred to as hypothyroidism. Hypothyroidism can cause weight gain, constipation, dry skin, tiredness and abnormal menstrual cycles.

High levels of TSH in the blood may indicate an overactive thyroid gland, commonly referred to as hyperthyroidism.  Hyperthyroidism can cause weight loss, increased heart rate, diarrhea, and abnormal menstrual cycles.