Endocrine Abstracts

Hypothyroidism (including subclinical hypothyroidism) occurs in about 2.5% of pregnancies. During pregnancy, maternal thyroid hormone requirements increase. It is known that the pregnant woman is the sole source of the fetal supply of thyroid hormones from conception to approximately 13 weeks of gestation when fetal thyroid function has developed. Organogenesis particularly of the nervous system is dependent on adequate thyroxine levels in fetal circulation. An elevated thyrot...