Hyperemesis with Thyroid Abnormalities

Hyperemesis with thyroid abnormalities is severe vomiting in early pregnancy with biochemical hyperthyroidism, a suppressed TSH and raised free T4. Most cases are gestational transient thyrotoxicosis caused by hCG stimulation of the thyroid, which settles by 14 to 18 weeks. It affects up to 60 percent of women with hyperemesis. It matters because it must be separated from Graves disease, which needs antithyroid drugs.

• Risk factors: severe hyperemesis, multiple pregnancy, molar pregnancy.
• Thyroid antibodies are absent in the transient form.
• Treatment is aimed at the vomiting, not the thyroid.

Women have severe vomiting, weight loss, palpitations and sweating, with mild tachycardia. A goitre, eye signs and previous thyroid disease point to Graves disease.

• No eye signs in the transient form.
• Tremor and heat intolerance are mild.
• Differential diagnosis: Graves disease, toxic nodule, thyroiditis, gastroenteritis, hepatitis, molar pregnancy.
• Complications: dehydration, electrolyte disturbance, arrhythmia, thyroid storm in Graves disease, malnutrition.

The approach is to interpret thyroid tests for the stage of pregnancy and to look for Graves disease.

• TSH, free T4 and total or free T3; in the first trimester TSH below 0.1 mIU/L with raised free T4 suggests thyrotoxicosis.
• TSH receptor antibodies and thyroid peroxidase antibodies; positive receptor antibodies indicate Graves disease.
• Electrolytes, urea, creatinine, liver enzymes, ketones.
• Ultrasound of the pregnancy for molar change; thyroid ultrasound if a nodule or goitre is present.

The principle is to treat vomiting and dehydration for transient thyrotoxicosis and to start antithyroid drugs only for Graves disease.

• Supportive: admit if dehydrated; fluids and antiemetics; daily weight; recheck thyroid tests every 2 weeks.
• Pharmacological: thiamine 100 mg IV daily for 3 days before dextrose; sodium chloride 0.9 percent 1 litre IV over 1 to 2 hours then 1 litre over 4 to 6 hours with potassium chloride 20 mmol per litre; metoclopramide 10 mg IV 8-hourly (maximum 5 days); ondansetron 4 mg IV 8-hourly if needed; propranolol 10 to 20 mg oral 8-hourly for palpitations in severe cases for a short period only; for confirmed Graves disease give propylthiouracil 100 mg oral 8-hourly in the first trimester, then change to carbimazole 15 to 30 mg oral daily from 16 weeks, using the lowest dose that keeps free T4 at the upper limit of normal.
• Procedures: none.
• Special groups: women with Graves disease have TSH receptor antibodies measured at 20 to 24 weeks and fetal growth and heart rate scans because of risk of fetal thyrotoxicosis; women taking antithyroid drugs have white cell count checked if sore throat or fever develops.
• Red flags: heart rate above 120 per minute, fever above 38 degrees Celsius, agitation, confusion, vomiting that cannot be controlled.
• Follow-up: repeat TSH and free T4 every 2 to 4 weeks; transient thyrotoxicosis resolves by 14 to 18 weeks; endocrine review for Graves disease; postnatal thyroid tests at 6 weeks.