Brief Answer: Thyroid Detailed Answer: Once an under-active thyroid has been diagnosed correctly as a permanent condition, it requires life long thyroid medication. This applies regardless of gender. The levels and targets are the same for both sexes, women are more prone to thyroid problems in general than men. So the key question is whether your TSH was greater than normal ie out of range. Usually anything above 3.5 is considered abnormal even though many labs continue to print 4.5 or 5 as upper limit of normal. The free T4 levels also are useful is aiding the diagnosis. If they are below normal then it supports the diagnosis of 'hypothyroidism'. However, it is more important to determine whether this is likely to be permanent (ie caused by an auto immune condition called Hashimoto's) or temporary (ie caused by a bruising of the thyroid called thyroiditis, which has a chance of recovering to normal). Such a differentiation can be best made by seeing an endocrinologist, although doing a blood test called anti TPO and anti Thyroglobulin antibodies does help. Regarding symptoms, I can understand why you may not feel different off it. The reason is that the symptoms of an underactive thyroid can be subtle and non-specific, especially if the degree of 'hypothyroidism' is mild. It is generally advisable to treat this as well. However, the decision has to be made after a discussion between the individual and the endocrinologist

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