Thyroid dysfunction is common in the general population especially in women. All thyroid diseases are in fact more common in women than in men and may interfere with the reproductive system. Thyroid function and the gonadal axes are related throughout the woman's fertile period. The relationship between the two glands is mutual. In particular, thyroid hormones affect the reproductive function both directly and indirectly through several actions. Studies on the relationship between menopause and thyroid function are few and do not allow to clarify whether menopause has an effect on the thyroid regardless of aging. With aging, the main changes regarding thyroid physiology and function are: a reduction of thyroid iodine uptake, free thyroxine and free triiodothyronine synthesis and catabolism of free thyroxine while reverse triiodothyronine increases; the level of thyroid stimulating hormone remains normal with sometimes a tendency to higher limits. These changes are present in both sexes without distinction between males and females. The complexity of the relationships can be summarized in three aspects: thyroid status does not influence significantly the climacteric syndrome; menopause may modify the clinical expression of some thyroid diseases, particularly the autoimmune ones; thyroid function is not directly involved in the pathogenesis of the complications of menopause. However, coronary atherosclerosis and osteoporosis may be aggravated in the presence of hyperthyroidism or hypothyroidism. The effects of postmenopausal estrogen replacement on thyroxine requirements in women with hypothyroidism should be considered.