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Overview of thyroid disease in pregnancy


The evaluation and treatment of pregnant women with thyroid disease parallel that of nonpregnant women and men, but present some unique problems. An overview of thyroid physiology and disease during pregnancy is presented here. Some of the disorders reviewed below are discussed separately in individual topic reviews. (See "Hypothyroidism during pregnancy: Clinical manifestations, diagnosis, and treatment" and "Hyperthyroidism during pregnancy: Clinical manifestations, diagnosis, and causes" and "Hyperthyroidism during pregnancy: Treatment".)


The diagnosis of thyroid disease during pregnancy requires an understanding of the changes in thyroid physiology and thyroid function tests that accompany normal pregnancy.

Thyroid physiology — To meet the increased metabolic needs during a normal pregnancy, there are changes in thyroid physiology that are reflected in altered thyroid function tests [1]. The major changes in thyroid function during pregnancy are an increase in serum thyroxine-binding globulin (TBG) concentrations and stimulation of the thyrotropin (TSH) receptor by human chorionic gonadotropin (hCG).

Thyroxine binding globulin — During pregnancy, serum TBG concentrations rise almost two-fold because estrogen increases TBG production and TBG sialylation, which results in decreased clearance of TBG [2]. To maintain adequate free thyroid hormone concentrations during this period, thyroxine (T4) and triiodothyronine (T3) production by the thyroid gland must increase. Total T4 and T3 concentrations rise during the first half of pregnancy, plateauing at approximately 20 weeks of gestation, at which time a new steady state is reached and the overall production rate of thyroid hormones returns to prepregnancy rates. Thus, TBG excess leads to an increase in both serum total thyroxine (T4) and triiodothyronine (T3) concentrations. (See "Euthyroid hyperthyroxinemia and hypothyroxinemia".)

hCG and thyroid function — Human chorionic gonadotropin (hCG) is one of a family of glycoprotein hormones, including thyrotropin (TSH), with a common alpha-subunit and a unique beta-subunit. However, there is considerable homology between the beta-subunits of hCG and TSH. As a result, hCG has weak thyroid-stimulating activity [3]. In a human thyroid cell-culture assay, as an example, 1 microU of hCG was equivalent to 0.0013 microU of TSH [4].


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Literature review current through: Mar 2014. | This topic last updated: Oct 3, 2012.
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  1. Glinoer D. The regulation of thyroid function in pregnancy: pathways of endocrine adaptation from physiology to pathology. Endocr Rev 1997; 18:404.
  2. Ain KB, Mori Y, Refetoff S. Reduced clearance rate of thyroxine-binding globulin (TBG) with increased sialylation: a mechanism for estrogen-induced elevation of serum TBG concentration. J Clin Endocrinol Metab 1987; 65:689.
  3. Ballabio M, Poshychinda M, Ekins RP. Pregnancy-induced changes in thyroid function: role of human chorionic gonadotropin as putative regulator of maternal thyroid. J Clin Endocrinol Metab 1991; 73:824.
  4. Yamazaki K, Sato K, Shizume K, et al. Potent thyrotropic activity of human chorionic gonadotropin variants in terms of 125I incorporation and de novo synthesized thyroid hormone release in human thyroid follicles. J Clin Endocrinol Metab 1995; 80:473.
  5. Glinoer D, de Nayer P, Bourdoux P, et al. Regulation of maternal thyroid during pregnancy. J Clin Endocrinol Metab 1990; 71:276.
  6. Yeo CP, Khoo DH, Eng PH, et al. Prevalence of gestational thyrotoxicosis in Asian women evaluated in the 8th to 14th weeks of pregnancy: correlations with total and free beta human chorionic gonadotrophin. Clin Endocrinol (Oxf) 2001; 55:391.
  7. Goodwin TM, Montoro M, Mestman JH, et al. The role of chorionic gonadotropin in transient hyperthyroidism of hyperemesis gravidarum. J Clin Endocrinol Metab 1992; 75:1333.
  8. Lockwood CM, Grenache DG, Gronowski AM. Serum human chorionic gonadotropin concentrations greater than 400,000 IU/L are invariably associated with suppressed serum thyrotropin concentrations. Thyroid 2009; 19:863.
  9. Stagnaro-Green A, Abalovich M, Alexander E, et al. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid 2011; 21:1081.
  10. Dashe JS, Casey BM, Wells CE, et al. Thyroid-stimulating hormone in singleton and twin pregnancy: importance of gestational age-specific reference ranges. Obstet Gynecol 2005; 106:753.
  11. Stricker R, Echenard M, Eberhart R, et al. Evaluation of maternal thyroid function during pregnancy: the importance of using gestational age-specific reference intervals. Eur J Endocrinol 2007; 157:509.
  12. Gilbert RM, Hadlow NC, Walsh JP, et al. Assessment of thyroid function during pregnancy: first-trimester (weeks 9-13) reference intervals derived from Western Australian women. Med J Aust 2008; 189:250.
  13. Fitzpatrick DL, Russell MA. Diagnosis and management of thyroid disease in pregnancy. Obstet Gynecol Clin North Am 2010; 37:173.
  14. Lambert-Messerlian G, McClain M, Haddow JE, et al. First- and second-trimester thyroid hormone reference data in pregnant women: a FaSTER (First- and Second-Trimester Evaluation of Risk for aneuploidy) Research Consortium study. Am J Obstet Gynecol 2008; 199:62.e1.
  15. Lee RH, Spencer CA, Mestman JH, et al. Free T4 immunoassays are flawed during pregnancy. Am J Obstet Gynecol 2009; 200:260.e1.
  16. Soldin OP, Tractenberg RE, Hollowell JG, et al. Trimester-specific changes in maternal thyroid hormone, thyrotropin, and thyroglobulin concentrations during gestation: trends and associations across trimesters in iodine sufficiency. Thyroid 2004; 14:1084.
  17. Kahric-Janicic N, Soldin SJ, Soldin OP, et al. Tandem mass spectrometry improves the accuracy of free thyroxine measurements during pregnancy. Thyroid 2007; 17:303.
  18. Yue B, Rockwood AL, Sandrock T, et al. Free thyroid hormones in serum by direct equilibrium dialysis and online solid-phase extraction--liquid chromatography/tandem mass spectrometry. Clin Chem 2008; 54:642.
  19. Leung AM, Pearce EN, Braverman LE. Iodine content of prenatal multivitamins in the United States. N Engl J Med 2009; 360:939.
  20. Burrow GN, Fisher DA, Larsen PR. Maternal and fetal thyroid function. N Engl J Med 1994; 331:1072.
  21. Vulsma T, Gons MH, de Vijlder JJ. Maternal-fetal transfer of thyroxine in congenital hypothyroidism due to a total organification defect or thyroid agenesis. N Engl J Med 1989; 321:13.
  22. Bajoria R, Fisk NM. Permeability of human placenta and fetal membranes to thyrotropin-stimulating hormone in vitro. Pediatr Res 1998; 43:621.
  23. Roti E, Gnudi A, Braverman LE, et al. Human cord blood concentrations of thyrotropin, thyroglobulin, and iodothyronines after maternal administration of thyrotropin-releasing hormone. J Clin Endocrinol Metab 1981; 53:813.
  24. Krassas GE, Poppe K, Glinoer D. Thyroid function and human reproductive health. Endocr Rev 2010; 31:702.
  25. Davis LE, Lucas MJ, Hankins GD, et al. Thyrotoxicosis complicating pregnancy. Am J Obstet Gynecol 1989; 160:63.
  26. Sheffield JS, Cunningham FG. Thyrotoxicosis and heart failure that complicate pregnancy. Am J Obstet Gynecol 2004; 190:211.
  27. Casey BM, Dashe JS, Wells CE, et al. Subclinical hyperthyroidism and pregnancy outcomes. Obstet Gynecol 2006; 107:337.
  28. American College of Obstetricians and Gynecologists.. ACOG Practice Bulletin. Clinical management guidelines for obstetrician-gynecologists. Number 37, August 2002. (Replaces Practice Bulletin Number 32, November 2001). Thyroid disease in pregnancy. Obstet Gynecol 2002; 100:387.
  29. Abalovich M, Gutierrez S, Alcaraz G, et al. Overt and subclinical hypothyroidism complicating pregnancy. Thyroid 2002; 12:63.
  30. Krassas GE, Pontikides N, Kaltsas T, et al. Disturbances of menstruation in hypothyroidism. Clin Endocrinol (Oxf) 1999; 50:655.
  31. Hallengren B, Lantz M, Andreasson B, Grennert L. Pregnant women on thyroxine substitution are often dysregulated in early pregnancy. Thyroid 2009; 19:391.
  32. LaFranchi SH, Haddow JE, Hollowell JG. Is thyroid inadequacy during gestation a risk factor for adverse pregnancy and developmental outcomes? Thyroid 2005; 15:60.
  33. Leung AS, Millar LK, Koonings PP, et al. Perinatal outcome in hypothyroid pregnancies. Obstet Gynecol 1993; 81:349.
  34. Wasserstrum N, Anania CA. Perinatal consequences of maternal hypothyroidism in early pregnancy and inadequate replacement. Clin Endocrinol (Oxf) 1995; 42:353.
  35. Davis LE, Leveno KJ, Cunningham FG. Hypothyroidism complicating pregnancy. Obstet Gynecol 1988; 72:108.
  36. Stagnaro-Green A, Chen X, Bogden JD, et al. The thyroid and pregnancy: a novel risk factor for very preterm delivery. Thyroid 2005; 15:351.
  37. Pop VJ, Kuijpens JL, van Baar AL, et al. Low maternal free thyroxine concentrations during early pregnancy are associated with impaired psychomotor development in infancy. Clin Endocrinol (Oxf) 1999; 50:149.
  38. Haddow JE, Palomaki GE, Allan WC, et al. Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N Engl J Med 1999; 341:549.
  39. Idris I, Srinivasan R, Simm A, Page RC. Maternal hypothyroidism in early and late gestation: effects on neonatal and obstetric outcome. Clin Endocrinol (Oxf) 2005; 63:560.
  40. Allan WC, Haddow JE, Palomaki GE, et al. Maternal thyroid deficiency and pregnancy complications: implications for population screening. J Med Screen 2000; 7:127.
  41. Klein RZ, Haddow JE, Faix JD, et al. Prevalence of thyroid deficiency in pregnant women. Clin Endocrinol (Oxf) 1991; 35:41.
  42. Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: scientific review and guidelines for diagnosis and management. JAMA 2004; 291:228.
  43. Committee on Patient Safety and Quality Improvement, Committee on Professional Liability. ACOG Committee Opinion No. 381: Subclinical hypothyroidism in pregnancy. Obstet Gynecol 2007; 110:959.
  44. De Groot L, Abalovich M, Alexander EK, et al. Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2012; 97:2543.
  45. Horacek J, Spitalnikova S, Dlabalova B, et al. Universal screening detects two-times more thyroid disorders in early pregnancy than targeted high-risk case finding. Eur J Endocrinol 2010; 163:645.
  46. Bussen S, Steck T. Thyroid autoantibodies in euthyroid non-pregnant women with recurrent spontaneous abortions. Hum Reprod 1995; 10:2938.
  47. Prummel MF, Wiersinga WM. Thyroid autoimmunity and miscarriage. Eur J Endocrinol 2004; 150:751.
  48. Männistö T, Vääräsmäki M, Pouta A, et al. Perinatal outcome of children born to mothers with thyroid dysfunction or antibodies: a prospective population-based cohort study. J Clin Endocrinol Metab 2009; 94:772.
  49. Chen L, Hu R. Thyroid autoimmunity and miscarriage: a meta-analysis. Clin Endocrinol (Oxf) 2011; 74:513.
  50. Thangaratinam S, Tan A, Knox E, et al. Association between thyroid autoantibodies and miscarriage and preterm birth: meta-analysis of evidence. BMJ 2011; 342:d2616.
  51. Negro R, Formoso G, Mangieri T, et al. Levothyroxine treatment in euthyroid pregnant women with autoimmune thyroid disease: effects on obstetrical complications. J Clin Endocrinol Metab 2006; 91:2587.
  52. Toulis KA, Goulis DG, Venetis CA, et al. Risk of spontaneous miscarriage in euthyroid women with thyroid autoimmunity undergoing IVF: a meta-analysis. Eur J Endocrinol 2010; 162:643.
  53. Negro R, Mangieri T, Coppola L, et al. Levothyroxine treatment in thyroid peroxidase antibody-positive women undergoing assisted reproduction technologies: a prospective study. Hum Reprod 2005; 20:1529.
  54. Ghassabian A, Bongers-Schokking JJ, de Rijke YB, et al. Maternal thyroid autoimmunity during pregnancy and the risk of attention deficit/hyperactivity problems in children: the Generation R Study. Thyroid 2012; 22:178.
  55. Smyth PP, Hetherton AM, Smith DF, et al. Maternal iodine status and thyroid volume during pregnancy: correlation with neonatal iodine intake. J Clin Endocrinol Metab 1997; 82:2840.
  56. Rasmussen NG, Hornnes PJ, Hegedüs L. Ultrasonographically determined thyroid size in pregnancy and post partum: the goitrogenic effect of pregnancy. Am J Obstet Gynecol 1989; 160:1216.
  57. Rotondi M, Amato G, Biondi B, et al. Parity as a thyroid size-determining factor in areas with moderate iodine deficiency. J Clin Endocrinol Metab 2000; 85:4534.
  58. Berghout A, Wiersinga W. Thyroid size and thyroid function during pregnancy: an analysis. Eur J Endocrinol 1998; 138:536.
  59. Kung AW, Chau MT, Lao TT, et al. The effect of pregnancy on thyroid nodule formation. J Clin Endocrinol Metab 2002; 87:1010.
  60. Glinoer D, Soto MF, Bourdoux P, et al. Pregnancy in patients with mild thyroid abnormalities: maternal and neonatal repercussions. J Clin Endocrinol Metab 1991; 73:421.
  61. Karger S, Schötz S, Stumvoll M, et al. Impact of pregnancy on prevalence of goitre and nodular thyroid disease in women living in a region of borderline sufficient iodine supply. Horm Metab Res 2010; 42:137.
  62. Tan GH, Gharib H, Goellner JR, et al. Management of thyroid nodules in pregnancy. Arch Intern Med 1996; 156:2317.
  63. Marley EF, Oertel YC. Fine-needle aspiration of thyroid lesions in 57 pregnant and postpartum women. Diagn Cytopathol 1997; 16:122.
  64. Rosen IB, Walfish PG, Nikore V. Pregnancy and surgical thyroid disease. Surgery 1985; 98:1135.
  65. Smith LH, Danielsen B, Allen ME, Cress R. Cancer associated with obstetric delivery: results of linkage with the California cancer registry. Am J Obstet Gynecol 2003; 189:1128.
  66. Moosa M, Mazzaferri EL. Outcome of differentiated thyroid cancer diagnosed in pregnant women. J Clin Endocrinol Metab 1997; 82:2862.
  67. Yasmeen S, Cress R, Romano PS, et al. Thyroid cancer in pregnancy. Int J Gynaecol Obstet 2005; 91:15.
  68. Herzon FS, Morris DM, Segal MN, et al. Coexistent thyroid cancer and pregnancy. Arch Otolaryngol Head Neck Surg 1994; 120:1191.
  69. Monroy-Lozano BE, Hurtado-López LM, Zaldivar-Ramírez FR, Basurto-Kuba E. [Clinical behavior of thyroid papillary cancer in pregnancy: optimal time for its treatment]. Ginecol Obstet Mex 2001; 69:359.
  70. Alves GV, Santin AP, Furlanetto TW. Prognosis of thyroid cancer related to pregnancy: a systematic review. J Thyroid Res 2011; 2011:691719.
  71. Nam KH, Yoon JH, Chang HS, Park CS. Optimal timing of surgery in well-differentiated thyroid carcinoma detected during pregnancy. J Surg Oncol 2005; 91:199.
  72. American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer, Cooper DS, Doherty GM, et al. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 2009; 19:1167.
  73. Chong KM, Tsai YL, Chuang J, et al. Thyroid cancer in pregnancy: a report of 3 cases. J Reprod Med 2007; 52:416.
  74. Kuy S, Roman SA, Desai R, Sosa JA. Outcomes following thyroid and parathyroid surgery in pregnant women. Arch Surg 2009; 144:399.
  75. Leboeuf R, Emerick LE, Martorella AJ, Tuttle RM. Impact of pregnancy on serum thyroglobulin and detection of recurrent disease shortly after delivery in thyroid cancer survivors. Thyroid 2007; 17:543.
  76. Rosário PW, Barroso AL, Purisch S. The effect of subsequent pregnancy on patients with thyroid carcinoma apparently free of the disease. Thyroid 2007; 17:1175.
  77. Hirsch D, Levy S, Tsvetov G, et al. Impact of pregnancy on outcome and prognosis of survivors of papillary thyroid cancer. Thyroid 2010; 20:1179.
  78. Nicholson WK, Robinson KA, Smallridge RC, et al. Prevalence of postpartum thyroid dysfunction: a quantitative review. Thyroid 2006; 16:573.
  79. Stagnaro-Green A. Postpartum thyroiditis. Best Pract Res Clin Endocrinol Metab 2004; 18:303.
  80. Caixàs A, Albareda M, García-Patterson A, et al. Postpartum thyroiditis in women with hypothyroidism antedating pregnancy? J Clin Endocrinol Metab 1999; 84:4000.
  81. Galofré JC, Haber RS, Mitchell AA, et al. Increased postpartum thyroxine replacement in Hashimoto's thyroiditis. Thyroid 2010; 20:901.