I-131 Treatment of Graves' Disease in an Unsuspected First Trimester Pregnancy; the Potential for Adverse Effects on the Fetus and a Review of the Current Guidelines for Pregnancy Screening

Radioactive iodine thyroid ablation has been shown to be an inexpensive, safe, and effective treatment for hyperthyroidism [1]. It is the most commonly used method for treating adult patients with Graves' disease [2]. It is very important not to treat a woman who is pregnant or nursing. Special precautions must be used in women of child-bearing age because of the possible detrimental side effects of fetal exposure [3].The American College of Radiology (ACR) practice guideline for the performance of therapy with unsealed radiopharmaceutical sources states that pregnancy should be ruled out using one of the following four criteria: (1) a negative hCG test obtained within 72 hours prior to administration of the radiopharmaceutical, (2) documented history of hysterectomy, (3) a postmenopausal state with absence of menstrual bleeding for two years, and (4) premenarche in a child age of 10 years or younger [4]. The Society of Nuclear Medicine (SNM) procedure guideline for therapy of thyroid disease with I-131 states that females of child-bearing age should routinely be tested for pregnancy within 72 hours or less before I-131 treatment. When the patient's history clearly indicates that pregnancy is impossible, the treating physician may omit the pregnancy test [5].TJ (not the patient's initials) is an adult female diagnosed with Graves' disease, which was treated with I-131 therapy in December 2004. She had been doing well until June 2006 when she presented to the pediatric endocrinology clinic with reoccurrence of her disease. Her thyroid function tests showed TSH < 0.03 (normal 0.32–5.0？munit/mL), free T4 2.80 (normal 0.71–1.85？ng/dL), and T4 19.1 (normal 5.0–12.0？mcg/dL). Unfortunately, her menstrual history was not documented during this clinic visit. TJ was scheduled for a radioactive iodine uptake and scan with subsequent ablation with I-131. A qualitative urine pregnancy test was performed 24 hours prior to ablation and was negative. A radioiodine uptake and scan r