goitre
description
thyroid enlargement, may be associated with hypo- or hyperthyroidism. hyperthyroid goitre is invariably due to transplacental passage of maternal thyroid-stimulating antibodies, whether or not the mother has clinically active graves’ disease. 1% of pregnant women will have graves’ disease, but only a small proportion (2 to 12%) of the fetuses will develop a goitre. hypothyroid goitres are of two aetiological types, acquired and genetic. acquired goitrous hypothyroidism occurs in three circumstances: secondary to transplacental passage of maternal antibodies that block the tsh-receptor site on the thyroid follicular cell; transplacental passage of goitrogens such as iodides or iodide containing drugs, including contrast agents and thionamides, used in the treatment of maternal hyperthyroidism; secondary to maternal iodine deficiency. genetic goitrous hypothyroidism is due to inborn errors of thyroxine biosynthesis. these conditions are rare (1 in 25,000 to 1 in 50,000).
diagnosis
the fetal thyroid can be imaged by the middle of the second trimester. measurement of the thyroid is performed using an axial scan through the neck at the midlevel of the thyroid. electronic calipers are placed on the outer dimensions of the gland just inside the carotid vessels. an ellipse is formed which encompasses the body of the thyroid in transverse section. the widest diameter and circumference are recorded. normal values are reported (see bromley et al., 1992). a goitre will present as a bilobed solid neck mass with some echolucent areas. rarely, the goitre will be large enough to potentially cause dystocia or tracheal obstruction with polyhydramnios. hyperthyroid goitre may be accompanied by oligohydramnios, intrauterine growth retardation, and tachycardia. recently colour doppler has been used to assess fetal thyroid function with changes in signal following successful treatment of maternal hyperthyroidism.
differential diagnosis
cysts of the branchial cleft and thyroglossal duct are embryologic remnants occurring in characteristic locations. the former is found anterolateral to the carotid sheath, and the latter is located in the midline. both tend to be unilocular. teratoma has a complex echo pattern, with solid and cystic components. calcification may be present in both haemangioma and teratoma, however gross calcification is generally restricted to teratoma, and fine scattered calcification to haemangioma. solid masses of the neck include neuroblastoma, lipoma, salivary gland tumour, mesenchyme sarcoma and neurofibroma. a haemangioma is a cystic, solid or mixed mass. occasionally it will be accompanied by multiple internal homogeneous echogenic reflections, representing calcified areas which are small and widely scattered, unlike the gross calcification of a teratoma. cystic areas may be pulsatile and doppler velocimetry should demonstrate low-resistance blood flow through them.
sonographic features
a solid neck mass with some echolucent areas, in the midline
associated iugr, oligohydramnios, tachycardia
associated syndromes
- daneman
- pendred
- refetoff
- thyro-cerebro-renal
references
- schimke rn in: human malformations and related anomalies oxford university press: new york, p1022-3
- bromley b, frigoletto fd jr, cramer d, osanthanondh r, benacerraf br the fetal thyroid: normal and abnormal sonographic measurements j ultrasound med 11: 25-8
- hatjis cg diagnosis and successful treatment of fetal goitrous hyperthyroidism caused by maternal graves disease obstet gynecol 81: 827-9
- abuhamad az, fisher da, warsof sl, slotnick rn, pyle pg, wu s-y, evans a antenatal diagnosis and treatment of fetal hypothyroidism: case report and review of the literature ultrasound obstet gynecol 6: 368-371
- barone cm, van natta fc, kourides ia sonographic detection of fetal goitre, an unusual cause of hydramnios j ultrasound med 4: 625-
- weiner s, scharf ji, bolognese rj, librizzi rj antenatal diagnosis and treatment of fetal goitre j reprod med 24: 39-41
- perelman ah, johnson rl, clemons rd, finberg hj, clewell wh, trujillo l intrauterine diagnosis and treatment of fetal goitrous hypothyroidism j clin endocrinol metab 71: 618-621
- noia g, de santis m, bocci a, maussier ml, d’errico g, bianchi a, romagnoli c, masini l, caruso a, mancuso s early prenatal diagnosis and therapy of fetal hypothyroid goitre fetal diagn ther 7: 138-143
- davidson km, richards ds, schatz da, fisher da successful in utero treatment of fetal goitre and hypothyroidism nejm 234: 543-6
- cutler ea, bass j, romshe ca, hamoudi ab, boesel cp, bachman d, kontras sb, sotos jf a familial thyro-cerebral-renal syndrome: a newly recognised disorder bdoas xiv: 265-274