Transient Hyperthyroidism of Hyperemesis Gravidarum

Pregnant Woman Sitting on Bathroom Floor with Box of Tissues between Knees
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During the first trimester of pregnancy, a small percentage of women develop a form of hyperthyroidism triggered by severe morning sickness. This morning sickness is known as hyperemesis gravidarum. The related short-term hyperthyroidism is known as transient hyperthyroidism of hyperemesis gravidarum, or THHG for short.

Symptoms of Hyperemesis Gravidarum

If you are experiencing hyperemesis without the transient hyperthyroidism, your symptoms are likely to include: 

  • Prolonged or severe vomiting
  • Difficulty eating or drinking without vomiting 
  • Weight loss. Ultimately, you may have lost as much or more than 5 percent of your pre-pregnancy weight
  • Fatigue
  • Weakness
  • Excessive salivation
  • Lightheadedness
  • Fainting
  • Infrequent urination

Hyperemesis gravidarum can also cause imbalances in the electrolyte levels in your blood.

Is it Hyperthyroidism or Transient Hyperthyroidism of Hyperemesis Gravidarum (THHG)?

When you have hyperemesis gravidarum, blood tests may also show evidence of hyperthyroidism. Based on the results of those doctors, your doctor will typically diagnose THHG if your thyroid stimulating hormone (TSH) level is low or low-normal, your free T4 is slightly elevated, and your free T3 is normal.

In contrast, if you have typical hyperthyroidism during pregnancy, you would typically have a low TSH level, and clearly elevated free T4 and free T3 levels.  

There are also symptomatic ways to distinguish THHG from other types of hyperthyroidism in pregnant women:

  • severe vomiting is characteristic of THHG and not typical in hyperthyroidism
  • lack of a goiter (enlarged thyroid) is characteristic of THHG and not typical in hyperthyroidism.
  • lack of ophthalmopathy (eye-related thyroid symptoms) is characteristic of THHG and not typical in hyperthyroidism
  • lack of other "classic" hyperthyroidism symptoms such as tachycardia (a rapid heartrate greater than 100 beats/minute), diarrhea, muscle weakness, or tremor is characteristic of THHG


    Some cases of THHG require no thyroid-specific treatment, and the thyroid abnormalities may spontaneously resolve by the end of the second trimester.

    When symptoms are severe, however, thyroid treatment may take place, usually during the first trimester, and may consist of a short course of antithyroid drugs.

    As your pregnancy hormones normalize after your first trimester and by weeks 16 to 20 you may find that your hyperthyroid symptoms subside. Your TSH level may remain suppressed however, even while your thyroid function returns to normal. Treatment may then be able to be discontinued, and your thyroid function will typically return to normal before delivery.

    Managing Hyperemesis Gravidarum

    When THHG does not involve significant thyroid abnormalities, managing it is the same as for hyperemesis gravidarum. Your doctor will likely encourage the following approaches:

    • Sleeping and resting as much as possible, and asking for help with household duties, childcare, shopping, or cooking.
    • Eating what you can, when you can. With hyperemesis, some practitioners say not to worry about what you're eating, just eat whatever stays down, and give in to cravings. You can talk to your doctor about vitamins or other ways to ensure you are getting sufficient nutrition.
    • Staying as hydrated as possible is a priority. Drink small amounts all day long. Stay away from tart or sweet drinks.  Also, extremely cold drinks may make the nausea/vomiting worse.
    • Figuring out if there is a pattern to your sickness.  For example, if a completely empty stomach makes you feel awful, keep crackers by your bed so you can snack during the night.

    If your case is severe, there are some medications including metoclopramide (Reglan), antihistamines, and antireflux medications that are prescribed. These medications are considered relatively safe during pregnancy and may help with the nausea.

    Each medicine has its own set of side-effects, so consult your doctor prior to taking any medication. Do not take any over-the-counter medicines without first discussing it with your doctor.

    When your nausea and vomiting are severe, you can become dehydrated and malnourished. This can also slow down your baby's weight gain and development in utero. Severe symptoms, therefore, may require that you be hospitalized to receive intravenous fluids (IV), nutrition, and anti-nausea medications. 

    On the alternative front, dietary changes, acupressure or acupuncture treatments, hypnosis, and herbal remedies such as peppermint and ginger may help with your severe nausea and vomiting. Discuss these treatments with your doctor first, and an important tip: only consult with practitioners who have experience working with pregnant women.


    Lazarus, JH."Thyroid disorders associated with pregnancy: etiology, diagnosis, and management." Treatments in Endocrinology 2005;4(1):31-41.

    Braverman, MD, Lewis E., and Robert D. Utiger, MD. Werner and Ingbar's The Thyroid: A Fundamental and Clinical Text. 9th ed., Philadelphia: Lippincott Williams & Wilkins (LWW), 2005.