Abstract
Thyroid diseases are very common disorders in women, and thyroid hormones are crucial
players in many aspects of fetal growth and neurodevelopment, both of which are dependent
on an adequate supply of maternal thyroid hormones from early gestation onwards. It
is therefore very important to keep women euthyroid during gestation. Globally, hypothyroidism
is still frequently caused by iodine deficiency. In iodine sufficient areas, the most
common cause of hypothyroidism is thyroid autoimmunity with positive anti-thyroperoxidase
antibodies (anti-TPO) measurable in serum. It is well known that overt maternal and
fetal hypothyroidism must be avoided during gestation as well as before assisted fertility.
It is, however, less clear if milder forms or subclinical hypothyroidism requires
thyroxine replacement therapy. Screening for thyroid disease is not recommended by
guidelines, but case finding based on specific criteria form general practice among
endocrinologists and fertility specialists. There are many different factors to be
aware of including, how measurements and interpretations of the laboratory tests for
thyroid related hormones are complicated by a combination of changes due to the physiology
of pregnancy, and the difficulty of laboratory measurements to correct for these changes.
A pragmatic algorithm for the management has been suggested, but there are still many
inconsistencies and controversies in the field. Very importantly, all clinicians managing
thyroid diseases should be aware of this and discuss it with the female patients of
fertile age as soon as the diagnosis of hypothyroidism is made in order to avoid negligence
from the patient if she becomes pregnant.
Keywords
Subclinical hypothyroidism - Fertility - Gestation - Thyroxine replacement - Thyroid
autoimmunity
