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2000-05-26-05 Answer of case of the week #26 © Sleurs www.TheFetus.net

Answer to case #26

May 26 - June 9, 2000

Submitted and discussed by Elke Sleurs, MD, Luc De Catte, MD 
Academic Hospital, Dept. of Obstetrics and Gynecology, Free University of Brussels, Laarbeeklaan 101, 1090 Brussels, Belgium

This G3P2 mother  which is treated for an endocrinological condition is at 32 week in the current pregnancy and has delivered 2 normal previous children. This fetus is referred for a second opinion because of fetal hydrocephaly. The ultrasound scan revealed a bilateral ventriculomegaly (not shown) secondary to a lumbo-sacral meningomyelocoele (not shown). These are a few images obtained during the examination as well as a 830 kb video-clip

Findings

This fetus showed a homogeneous and hypoechogenic mass, situated at both sides of the trachea. The mass is situated at the anterior aspect of the neck. Since the mother suffers from an endrocine disorder, a fetal goiter should be considered as the most likely diagnosis.

Case report

This 33-year-old female received 100 mg propylthiouracil and thyroxin 0.1 mg daily for a poorly documented maternal Graves’ disease for several years. Due to poor prenatal follow-up she was only referred at 32 weeks of gestation for suspicion of fetal hydrocephaly. The ultrasound scan revealed bilateral ventriculomegaly secondary to a lumbo-sacral meningomyelocele and an anteriorly located neck-mass suggestive for a fetal goiter. Maternal blood samples showed a decreased TSH (0.101 mIU/L Normal: 0.2-5.0mIU/L) with normal FT4 and FT3. Fetal goiter due to fetal hypothyroidism (TSH = 23.044 mIU/L; FT3 = 1.3 ng/L= 0.844pmol/L; FT4 =13.2 ng/L= 0.1 pmol/L) was confirmed by fetal blood sampling. 150 micrograms of L-Thyroxine was injected into the amniotic cavity twice, at one-week intervals, resulting in a decrease of fetal TSH levels. Because of psychological distress, labor was induced at 37 weeks of gestation. The baby died 8 days later.

Discussion

Although prenatal diagnosis of fetal goiter is rare [1] , [2] [3] [4] , timely recognition and treatment is essential to achieve optimal growth and neurological development.

Abnormal fetal thyroid function may have severe consequences on fetal development. It is associated with considerable neonatal mortality and long-term morbidity. Untreated fetal hypothyroidism may result in mental retardation, perceptual-motor, visual-spatial, and language development problems. Moreover, fetal hypothyroidism is associated with fetal growth retardation, congenital heart block cardiomegaly and delayed skeletal maturation [5] . Furthermore, a large goiter causes hyperextension of the neck resulting in malpresentation, obstruction of the trachea, esophageal compression and polyhydramnios, and asphyxia and fetal death1 ,2 .

Etiology

Recognition of risk factors may increase the detection of fetal goiter [6] :

·         previous therapy for hyperthyroidism,

·         previous high-dose neck irradiation,

·         previous post-partum thyroiditis (evidence of thyroid autoimmune disease),

·         goiter (diffuse or nodular),

·         family history of thyroid disease,

·         treatment with amiodarone,

·         suspected hypopituitarism, type I maternal diabetes.

At a more moderate risk are patients with any other endocrinopathy, autoimmune disorder, hyperlipidemia, medication or exposure to some industrial and environmental chemicals.

Fetal goiter can be the result of either hypo– or hyperthyroidism.

Transient fetal hypothyroidism is most frequently associated with maternal antithyroid drug ingestion, commonly propylthiouracil (PTU) or carbimazol for Graves’ disease1 ,3 , [7] , [8] .  PTU prevents the synthesis of thyroid hormones and inhibits peripheral deiodination of T4 to T3. As PTU crosses the placenta it can cause fetal hypothyroidism. The incidence is approximately 12%. PTU-induced goiters are not predictable or dose-dependent, but the smallest possible dose should be used especially in the third trimester. In the patients, maternal FT4 should be kept in the upper normal range to minimize the chance for fetal hypothyroidism5 . The limited use of PTU early in the first trimester of pregnancy will not lead to a fetal goiter because the fetal thyroid hormone synthesis does not start not until the 11th or 12th week of gestation8 . Other causes of fetal hypothyroidism are the use of I131 in pregnant women, the administration (maternal or fetal) of amiodarone for fetal supraventricular tachycardia [9] and maternal intake of lithium.

Fetal hyperthyroidism on the other hand is almost invariably secondary to maternal autoimmune disorders. Graves’ disease is characterized by the presence of several thyroid-stimulating immunoglobulins, including those directed against TSH receptors in the thyroid gland. As these antibodies are of the IgG subclass, they will cross the placenta and cause hyperthyroidism5 , [10] .

Diagnosis

The ultrasound diagnosis of fetal goiter can easily be made by routine transverse and sagittal scanning of the neck region. A transverse scan through the fetal neck can reveal the presence of an anteriorly localized cervical mass, present at both sides of the trachea, and usually homogeneous and anechogenic. A large goiter causes hyperextension of the neck. Normograms for the transverse diameter and the circumference of fetal thyroid gland are available [11] .

Differential diagnosis

The most important differential diagnoses are cervical teratoma and hemangioma. Cervical teratoma is usually a mixed solid-cystic mass originating from the thyroid region. It is often rapidly growing, and associated with polyhydramnios because of esophageal compression. Thyroid function is usually not disturbed in utero, but hypothyroidism becomes relevant after surgical excision of the teratoma.

Lymphangioma or hemangioma of the cervical region are rare and originate mostly from the lateral part of the neck. The cystic components are more prominent. Hygroma colli involves occasionally the lateral part of the neck, but is more often localized posteriorly. 

Therapy

In case of ultrasonic suspected fetal thyroid disease, fetal therapy depends on the diagnosis of the thyroid condition5 ,10 , [12] , [13] .

Since in case of maternal Graves’ disease the fetal goiter can be the result of transplacental passage of the antithyroid drugs or the passage of thyroid-stimulating antibodies. As amniotic fluid analysis of thyroid hormone and TSH are not reliable, fetal thyroid status can only be determined by fetal blood sampling1 ,5 ,10 ,12 .

In case of fetal hyperthyroidism the management requires optimizing maternal thyroid status by adapting maternal therapy. Normalization of fetal thyroid function can be evaluated by color Doppler ultrasound: the intensified color Doppler signal disappears with intensified maternal treatment [14] .

In case of fetal hypothyroidism additional therapy can be necessary. Although the mechanism of actions of T4 in amniotic fluid is unclear, direct intra-amniotic administration of 150 – 500 mg L-Thyroxine weekly will decrease fetal goiter and normalize fetal thyroid function4 ,5 ,10 . Indirect prenatal therapy by administration of a thyroid analogue seems promising [15] .

References:

[1] HA Hadi, D Strickland. In utero treatment of fetal goitrous hypothyroidism caused by maternal graves’ disease. Am J Perinatol 1995;12(6):455-58

[2] AZ Abuhamad, DA Fisher, SL Warsof et al: Antenatal diagnosis and treatment of fetal goitrous hypothyroidism: case report and review of the literature. Ultrasound Obstet Gynecol 1995;6:368-71.

[3] AJ Van Loon, JT Derksen, AF Bos et al. In utero diagnosis and treatment of fetal goitrous hypothyroidism, caused by maternal use of propylthiouracil. Prenat Diagn 1995; 15:599-604.

[4] JP Bruner, EH Dellinger. Antenatal diagnosis and treatment of fetal hypothyroidism. Fetal Diagn Ther 1997;12:200-4.

[5] JG Thorpe-Beeston. Goitre. In: Fetal therapy, invasive and transplacental. Ed NM Fisk and KJ Moise 1997, pag 252-260.

[6] MN Montoro. Management of hypothyroidism during pregnancy. Clinic Obstet Gynecol 1997;40(1):65-80.

[7] N Momotani, JY Noh, N Ishikawa, K Ito: Effects of prpylthiouracil and methimazole on fetal thyroid status in mothers with Graves’ hyperthyroidism. J Clin Endocrinol Metab 1997; 82: 3633-6.

[8] G Briggs, K Freeman, S J Yaffe. Drugs in pregnancy and lactation.

[9] L. De Catte, D. De Wolf, J. Smitz, et al. Fetal hypothyroidism as a complication of amiodarone treatment for persistent fetal supraventricular tachycardia. Prenat.Diagn.1994;14:00-04.

[10] JG Thorpe-Beeston, KH Nicolaides. Maternal and fetal thyroid function in pregnancy. Frontiers in fetal medicine series. Ed KH Nicolaides. Parthenon Publishing, 1996.

[11] B Bromley, FD Frigoletto, D Cramer et al. The fetal thyroid: normal and abnormal measurements. J Ultrasound Med 1992;11:25-8.

[12] DA Fisher. Fetal thyroid function: diagnosis and management of fetal thyroid disorders. Clinic Obstet Gynecol 1997;40(1):16-31.

[13] AH Perelman, RD Clemons. The fetus in maternal hyperthyroidism. Thyroid 1992;2:225-8.

[14] D Luton, D Fried, O Sibony et al. Assessment of fetal thyroid function by colored Doppler echography. Fetal Diagn Ther 1997;12:24-7.

[15] U Nicolini, E Venegoni, B Acaia, D Cortelazzi, P Beck-Peccoz. Prenatal treatment of fetal hypothyroidism: is there more than one option? Prenat Diagn 1996;16(5):443-8

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