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Gestational Hypertyroidism?

Last Updated: · Doctors


I would appreciate you comments on a young woman RDW age 35 years. I saw her first on June 13, 2003, when she was 33 weeks pregnant. On June 3, 2003, her free T4 was 11.3 pmol/L (7.5 ' 21.1). Her free T3 was 5.6 (2.3 ' 6.3), and her TSH was 0.16. At about 16 weeks she had noticed shortness of breath and tachycardia which was episodic when at work, and this would last from 5 ' 30 minutes. There was an abrupt onset and a less abrupt cessation with the tachycardia. It was regular. She had been previously diagnosed with polycystic ovarian disease and had irregular menses.

Her grandmother had had a thyroid problem and had a thyroid operation. Her grandfather's sister had thyroid disease. Her paternal grandfather died at 65 of heart disease, and her maternal grandfather died of congestive heart failure at 96 years.Her father came from Germany and moved to Newfoundland after the Second World War.She had had a diabetes screen, and that was normal.

On examination at that time, her blood pressure was 100/60, and her heart rate was 92 per minute. Her thyroid was slightly enlarged, and there was no tremor and no eye signs.

On June 16, 2003, her free T4 was 9.8, free T3 4.0, and TSH 0.48. She felt well. She still had a tachycardia of 108 per minute.

On July 4, 2003, her free T4 was 10.2 and TSH 0.13. Because of her uncomfortable symptoms of tachycardia, I started her on Inderal 10 mg t.i.d.

On July 11, 2003, her free T4 was 10.7, free T3 4.2, and TSH 0.25, and her heart rate was 80 per minute.

The baby was born on July 25, 2003, and there were no problems.

When I saw her on August 5, 2003, I noted a 1 cm nodule in the right thyroid lobe and referred her to a thyroid surgeon who did a fine needle aspiration biopsy on August 12, 2003. This was interpreted as a nodular goitre with cystic degeneration. At that time the free T4 was 13.2 and TSH 0.13, and her heart rate was 84 per minute.

On January 15, 2004, a thyroid scan showed a diffuse uptake with a hotter nodule in the lower pole of the right lobe. This nodule did not suppress the uptake in the rest of the gland.

On January 15, 2004, her free T3 was 4.7, free T4 11.2, and TSH 0.34.

On June 17, 2004, she was feeling tired, still had brief tachycardia, and on May 21, 2004, her free T4 was 12.5 (7.5 ' 21.1), free T3 3.7 (2.3 ' 6.3), and TSH 0.26. Her thyroglobulin and peroxidase antibodies were negative. Her baby at this time was 11 months old.

On December 9, 2004, when she was feeling well, her free T4 was 12.7, free T3 4.0, and TSH 0.31.

There was a small nodule in the lower pole of the right thyroid, and this was biopsied again and yielded chocolate fluid.

On August 3, 2005, her free T4 was 12.5 and TSH 0.39. She had had another fine needle aspiration bipsy, which showed nodular goitre with cystic degeneration.

In November 2005, she had started Ortho Tri-Cyclen because of her complexion, and after this, she had a number of symptoms, which in retrospect may have been due to the Ortho Tri-Cyclen because they went away when it was stopped.

On August 14, 2006, she had noticed tachycardia and was short of breath, at this time her free T4 was 13.0, and her TSH was 0.28.

On April 13, 2007, her free T4 was 11.6, free T3 4.0, and TSH 0.34.

When I saw her again on June 5, 2007, she was eight weeks pregnant with twins. On May 31, 2007, her free T4 was 15.0 (new normal range of 7.8 ' 16.0), free T3 4.8, and TSH 0.10. Thyrotropin receptor and thyroglobulin and peroxidase antibody levels were normal.She had a lot of nausea and was taking Diclectin. Her heart rate was increased to 110 per minute. On June 6, 2007, she was started on Inderal 10 mg t.i.d. and later this was increased to 20 mg t.i.d.

On July 10, 2007, her free T4 was 18.8 (7.8 ' 16.0), free T3 5.4 (3.2 ' 5.0), and TSH 0.02. She was feeling good at this time on Inderal 20 mg t.i.d.

On July 13, 2007, I started her on PTU 50 mg t.i.d., and she continued the Inderal 20 mg t.i.d.

On July 25, 2007, her free T4 was 15.7, free T3 4.7, and TSH 0.07, and she was feeling well.

On August 12, 2007, her free T4 was 10.6, free T3 3.8, and TSH 0.06.On August 15, 2007, I told her to stop the PTU. At this time, she was 18 weeks pregnant.

On August 17, 2007, her free T4 was 9.8, free T3 4.4, and TSH 0.03, and she was not taking PTU.

On August 23, 2007, her free T4 was 9.1, free T3 3.6, and TSH 0.04.

On September 6, 2007, her free T4 was 7.6, free T3 3.7, and TSH 0.11. She continued Inderal 10 mg t.i.d. but was not taking any Propylthiouracil.

On September 18, 2007, her free T4 was 7.0 (7.8 ' 16.0 pmol/L), free T3 2.5 (3.2 ' 5.0 pmol/L), and TSH 0.16.

She continues to feel well on a small dose of Inderal and no Propylthiouracil since August 15, 2007.

My differential all along has been gestational thyrotoxicosis, most likely with a differential of toxic nodular goitre. I have asked our lab to send blood off for a total T4, because I believe the free T4 and free T3 levels may be misleading because of her high level of thyroixin binding globulin.

D. W. Ingram, MB, FRCPC, FACP
St. Clare's Mercy Hospital, St. John's, NL A1C 5B8


  1. Long and detailed case history of a 35 year old woman who was first pregnant in 2003 (singleton). Basically, thyroid function tests were normal during her pregnancy, except for a slightly decreased serum TSH (not constantly though) between 0.16 and 0.48 mU/L, at gestational ages varying between 33 weeks and parturition. Treatment given was Inderal (I would not have treated her). Normal and full-term delivery.
  2. After delivery, further work up disclosed a nodular goiter with cystic degeneration as well as a "hotter" nodule in the lower right lobe of the thyroid, with normal thyroid function tests and negative thyroid antibodies. FNA revealed chocolate fluid, consistent with hematic cystic nodular lesion.
  3. Two thyroid function tests, carried out in 2006 and 2007 (before her next pregnancy) showed normal thyroid function tests and again a slightly decreased serum TSH (0.28 and 0.34 mU/L) consistent with the probable presence of autonomous tissue within the goiter.
  4. In June 2007, the patient was 8 weeks pregnant (this time with a twin pregnancy) and developed Gestational Hyperthyroidism with excessive nausea and vomiting (?). For the first time, thyroid function tests revealed moderate hyperthyoidism, with serum free T4 and free T3 levels slightly above the upper limit of normality and serum TSH still measurable but clearly decreased at 0.02 mU/L. Patient received Inderal and PTU; PTU was stopped after one month.

My comments are that this case illustrates biochemical and clinical evidence of Gestational Transient Thyrotoxicosis related to twin pregnancy (see Chapter 14 of the Thyroid Disease Manager), presumably aggravated by the presence of a nodular goiter, perhaps containing autonomous tissue. The issue of treating these patients with PTU is highly debatable.

Prof Daniel Glinoer