After having reviewed briefly the main characteristics of adult thyroid function, as well as the ways in which this is controlled (the first part), the authors reviewed present day methods of investigating thyroid gland function (the second part). In the third part of the work hormonal interrelationships between the thyroid and the ovary are discussed as well as the influence of gonadal hormones on thyroid function and the influence of the latter on ovarian function and on hypothalamic-pituitary interactions. The effects of thyroid diseases on reproductive function are studied in the last part of the work.