How to Manage Fetal Hypothyroidism and Goiter


Question

Dear expert: Patient is a 29 yr old lady - 26 weeks intauterine pregnant. She has had an earlier miscarriage at 6 wks gestation - cause unknown. Not a consanguinous marriage. Routine ultrasound at 26 weeks revealed a fetal goiter - 3.5 x 2.5x 2.5 cms. Weeks of gestation by ultrasound corresponds to gestational age by LMP. Pregnancy is otherwise normal without any other complications. There are not from endemic areas for iodine deff.Mother's thyroid function tests are normal - TSH and Free T4 . Her Antithyroid peroxidase antibodies are negative. Cord blood TSH is > 100, Free T4 - 2.5 (4.2 - 6.2),Anti TPO is negative. IV levothyroxine is avialable with difficulty and very expensive - Rs 8000/ per 100 Ucg. These are mothers and my concerns :

1) Will the baby's IQ be completely normal with treatment with intra-amniotic LT4?

2) What are the chances of a similar problem in subsequent pregnancies - as she is considering an MTP if the chance of normalization OF IQ of the child is not high.

Other queries are:

1) What would be the dose of IV levothyroxine -intra-amniotic - would a loading dose be required?

2) How soon would the goiter shrink and will it shrink completely???

3) Would oral LT4 in high doses be of any use at all, since cost is a factor?

4) Would u recommend an MTP to this patient?

We would appreciate a prompt response so that a decision can be made soon.

Regards,

Radha Reddy MD (Endocrinology and Diabetes, USA), Consultant Endocrinologist,

Mallya Hospital, Bangalore, India

"radha reddy" < radreddy@yahoo.com >, Thursday, June 06, 2002 8:58 PM

Response

Dear Dr. Reddy: I find your case most unique and perplexing since the baby appears to have quite severe fetal hypothyroidism despite the apparent absence of either thyroid disease or medication in the mother. Therefore, one would need to hypothesize both fetal thyroid disease (presumably due to an abnormality of thyroid hormonogesis) as well as the absence of adequate maternal thyroid hormone to at least partially compensate for the severe fetal hypothyroidism. I would therefore think that before embarking on intraamniotic T4, it is most important to be absolutely sure that the mother is not taking something (e.g., a homeopathic remedy, or iodine-containing medicine for asthma, etc.) that might preferentially affect the baby's thyroid function.

In answer to your questions:

1)Although there are no guarantees in medicine, the baby's IQ should be normal with intramniotic T4. By analogy, babies with no thyroid gland at all have normal cognitive development even with POSTnatal treatment as long as treatment is sufficiently early and adequate. I personally have never advocated intraamniotic T4 since usually my preference would be to reduce the dosage of antithyroid medication in the mother (in cases of maternal Graves' disease). I would, however, in your case due to the severity of the hypothyroidism, not to mention the presence of fetal goiter which, if sufficiently large, can cause respiratory obstruction and distress.

2) Most cases of thyroid dyshormonogenesis are autosomal recessive and therefore carry with them a 1/4 chance of recurrence in each pregnancy. It is now possible to determine the molecular etiology of many of these cases although this is usually only done in research laboratories and clearly, if the molecular etiology were known one could even do fetal diagnosis.

3) The doses of L-T4 that have been used in the literature are 250-500 micrograms, given every 1-2 weeks as necessary. Improvement in the TFT's and shrinkage of the goiter are observed within a few weeks. (cf: Perelman AH et al, JCEM 71:618, 1989;Davidson KM et al, NEJM 324:543, 1991;Vicens-Calvet E et al, J Pediatr 133: 147,1998).

4) Yes (see (1)

Sincerely, Rosalind S. Brown, MD,Professor of Pediatrics,

University of Massachusetts Medical School,

Director, Division of Pediatric Endocrinology/Diabetes

UMass Memorial Health Care <Rosalind.Brown@umassmed.edu>