Breastfeeding and Thyroid Problems: Studies and References

(most recent listed first in each category)

General

Hale TW. Medications and Mothers Milk, 15th Edition. Amarillo, Texas: Hale Publishing, 2012.

Lawrence R and Lawrence R. Breastfeeding: A Guide for the Medical Profession, 7th ed. St. Louis: Mosby, 2011, p. 570-574.

Riordan J, Wambach K. Breastfeeding and Human Lactation, 4th ed. Boston and London: Jones and Bartlett, 2010, p. 90, 147, 186-187, 522-523.

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Mohrbacher N. Breastfeeding Answers Made Simple. Amarillo, Texas: Hale Publishing, 2010, p. 262, 396, 414-416, 422, 767-769.

Effects of breastfeeding on maternal & child thyroid health

Mack WJ, Preston-Martin S, Bernstein L, Qian D, Xiang M. Reproductive and hormonal risk factors for thyroid cancer in Los Angeles County females. Cancer Epidemiol Biomarkers Prev 1999 Nov;8(11):991-7.

“…risk [of thyroid cancer] increased with number of pregnancies in women using lactation suppressants… and decreased with duration of breastfeeding.”

Smyth PP, Hetherton AM, Smith DF, Radcliff M, O’Herlihy C. Maternal iodine status and thyroid volume during pregnancy: correlation with neonatal iodine intake. J Clin Endocrinol Metab 1997 Sep;82(9):2840-3.

“The results suggest that in an area of moderate dietary iodine intake, urinary iodine loss during pregnancy may result in maternal thyroid enlargement. The ability of the breast to transport iodine compensates for this loss in breast-fed infants, but this protection may be lost in formula feeding.”

Bohles H, Aschenbrenner M, Roth M, von Loewenich V, Ball F, Usadel KH. Development of thyroid gland volume during the first 3 months of life in breast-fed versus iodine-supplemented and iodine-free formula-fed infants. Clin Investig. 1993 Jan;71(1):13-20.

Fort P, Moses N, Fasano M, Goldberg T, Lifshitz F. Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children. J Am Coll Nutr 1990 Apr;9(2):164-7.

Oberkotter LV, Hahn HB. Thyroid function and human breast milk (letter). Am J Dis Child 1983 Nov;137(11):1131.

Methimazole / Tapazole

Azizi F, Bahrainian M, Khamseh ME, Khoshniat M. Intellectual development and thyroid function in children who were breast-fed by thyrotoxic mothers taking methimazole. J Pediatr Endocrinol Metab. 2003 Dec;16(9):1239-43.

“Thyroid function and physical and intellectual development of breast-fed infants whose thyrotoxic lactating mothers were treated with 20-30 mg doses of MMI daily are normal at age 48 to 86 months.”

Azizi F. Thyroid function in breast-fed infants is not affected by methimazole-induced maternal hypothyroidism: results of a retrospective study. J Endocrinol Invest. 2003 Apr;26(4):301-4.

Azizi F, Hedayati M. Thyroid function in breast-fed infants whose mothers take high doses of methimazole. J Endocrinol Invest 2002 Jun;25(6):493-6.

“We conclude that the treatment of hyperthyroid lactating mothers with doses of 20-30 mg MMI day does not cause deleterious effects on thyroid function of their breast-fed infants.”

Azizi F, Khoshniat M, Bahrainian M, Hedayati M. Thyroid function and intellectual development of infants nursed by mothers taking methimazole. J Clin Endocrinol Metab. 2000 Sep;85(9):3233-8.

“…No deleterious effects occur in thyroid function and physical and intellectual development of breast-fed infants whose lactating mothers were treated with doses of MMI up to 20 mg daily.”

Azizi F. Effect of methimazole treatment of maternal thyrotoxicosis on thyroid function in breast-feeding infants. J Pediatr. 1996 Jun;128(6):855-8.

“In 35 infants of lactating mothers with thyrotoxicosis who were receiving 5 to 20 mg methimazole daily, serum levels of thyroxine, triiodothyronine, thyrotropin were within normal ranges 1 month after the start of breast-feeding. Thyroid function in breast-feeding infants of six lactating mothers receiving methimazole, 20 mg for the first, 10 mg for the second, and 5 mg for an additional 4 months, remained normal. These results suggest the safety of methimazole therapy in lactating mothers.”

Johansen K, Andersen AN, Kampmann JP, Molholm Hansen JM, Mortensen HB. Excretion of methimazole in human milk. Eur J Clin Pharmacol. 1982 Oct;23(4):339-41.

Propylthiouracil / PTU

Momotani N, Yamashita R, Makino F, Noh JY, Ishikawa N, Ito K. Thyroid function in wholly breast-feeding infants whose mothers take high doses of propylthiouracil. Clin Endocrinol (Oxf). 2000 Aug;53(2):177-81.

“…Mothers can breast-feed while taking propylthiouracil at doses as high as 750 mg daily without adverse effects on thyroid status in their infants.”

Lee A, Moretti ME, Collantes A, Chong D, Mazzotta P, Koren G, Merchant SS, Ito S. Choice of breastfeeding and physicians’ advice: a cohort study of women receiving propylthiouracil. Pediatrics. 2000 Jul;106(1 Pt 1):27-30.

Momotani N, Yamashita R, Yoshimoto M, Noh J, Ishikawa N, Ito K. Recovery from foetal hypothyroidism: evidence for the safety of breast-feeding while taking propylthiouracil. Clin Endocrinol (Oxf) 1989 Nov;31(5):591-5.

McDougall IR, Bayer MF. Should a woman taking propylthiouracil breast-feed? Clin Nucl Med. 1986 Apr;11(4):249-50.

Myres AW. Thyroid and antithyroid drugs and breast-feeding. CMAJ. 1987 May 1;136(9):921.

Kampmann JP, Johansen K, Hansen JM, Helweg J. Propylthiouracil in human milk. Revision of a dogma. Lancet. 1980 Apr 5;1(8171):736-7.

Low LC, Lang J, Alexander WD. Excretion of carbimazole and propylthiouracil in breast milk. Lancet. 1979 Nov 10;2(8150):1011.

Radioactive iodine (various isotopes)

Saenz RB. Iodine-131 elimination from breast milk: a case report. J Hum Lact. 2000 Feb;16(1):44-6.

This case report describes the management of a breastfeeding mother who had been given radioactive iodine and technetium for diagnosis of thyroid disease. The mother requested to submit weekly milk samples for monitoring of radioactivity. Once activity fell below measurable counts, the mother resumed lactation.

Morita S, Umezaki N, Ishibashi M, Kawamura S, Inada C, Hayabuchi N. Determining the breast-feeding interruption schedule after administration of 123I-iodide. Ann Nucl Med. 1998 Oct;12(5):303-6.

“123I was excreted exponentially with an effective half-life of 5.5 h; 2.5% of the total radioactivity administered was excreted in the breast milk over the 93 h, 95% of which was excreted within the first 24 h, and 98.2% within 36 h… According to our calculations, breast feeding should be curtailed for 36 h to reduce the infant’s exposure to 123I radioactivity.”

Robinson PS, Barker P, Campbell A, Henson P, Surveyor I, Young PR. Iodine-131 in breast milk following therapy for thyroid carcinoma. J Nucl Med 1994 Nov;35(11):1797-801.

Hedrick WR, Di Simone RN, Keen RL. Radiation dosimetry from breast milk excretion of radioiodine and pertechnetate. J Nucl Med. 1986 Oct;27(10):1569-71.

Thyroid cancer

“…risk [of thyroid cancer] increased with number of pregnancies in women using lactation suppressants… and decreased with duration of breastfeeding.”

Le Ber JD. Thyroid cancer, I131, and breastfeeding: one woman’s experience (Letter). J Hum Lact 1995 Sep;11(3):175.

Robinson PS, Barker P, Campbell A, Henson P, Surveyor I, Young PR. Iodine-131 in breast milk following therapy for thyroid carcinoma. J Nucl Med 1994 Nov;35(11):1797-801.

Thyroid hormones in breastmilk

van Wassenaer AG, et al. The quantity of thyroid hormone in human milk is too low to influence plasma thyroid hormone levels in the very preterm infant. Clin Endocrinol (Oxf). 2002 May;56(5):621-7.

“We investigated whether breast milk is a substantial resource of thyroid hormone for very preterm neonates and can alleviate transient hypothyroxinaemia. Both the influence of breast feeding on plasma thyroid hormone levels and the thyroid hormone concentration in preterm human milk were studied… No differences in plasma thyroid hormone between breast milk-fed and formula-fed infants were found. The amount of T4 present in human milk and formula milk is too low to alter the hypothyroxinaemic state of preterm infants.”

Robinson P, Hoad K. Thyrotropin in human breast milk. Aust N Z J Med 1994 Feb;24(1):68.

Thyrotropin (TSH) level in breastmilk was determined in a hypothyroid mother. The mother’s plasma TSH was 110 mU/L, but breastmilk TSH level was low (1.4 mU/L), suggesting that breastfeeding by hypothyroid mothers is permissable.

Mizuta H, Amino N, Ichihara K, Harada T, Nose O, Tanizawa O, Miyai K. Thyroid hormones in human milk and their influence on thyroid function of breast-fed babies. Pediatr Res. 1983 Jun;17(6):468-71.

“The serum levels of thyrotropin, T4, free T4 and T3 were not significantly different between breast-fed and bottle-fed babies. These results indicate that T3 excretion in milk cannot be explained by simple diffusion from the blood into the mother’s milk and that breast feeding has no influence on the pituitary thyroid axis of normal babies.”

Varma SK, Collins M, Row A, Haller WS, Varma K. Thyroxine, tri-iodothyronine, and reverse tri-iodothyronine concentrations in human milk. J Pediatr 1978 Nov;93(5):803-6.

Sack J, Amado O, Lunenfeld B. Thyroxine concentration in human milk. J Clin Endocrinol Metab 1977 Jul;45(1):171-3.