This article is more than 5 years old. Information may no longer be current.
Intramuscular thyroxine therapy?
Click Here to Manage Email Alerts
One of the endocrinologists with whom I work was called by an internal medicine colleague who practices in another state. The internist has a patient who is 31 weeks pregnant with a thyroid-stimulating hormone of 3.31 and a free T4 < 0.1. She is seeing an endocrinologist who has been treating her with intramuscular thyroxine therapy.
We have no other information regarding the patient or her situation. Is there non-compliance involved? Is there severe gastrointestinal malabsorption? I do not know.
The internist asked the endocrinologist with whom I work, “Have you ever heard of intramuscular thyroxine therapy? “
He had not. My colleague walked across the hall and asked me if I had ever heard of intramuscular thyroxine therapy. I had not heard of it either.
We must be careful, however. “I have never heard of it,” is not the same as “It does not exist,“ or “It has never been tried.” Too many physicians, when presented with something they have never heard of, assume it must not be true and fail to investigate further.
When in doubt, we should ask knowledgeable colleagues. Better yet, we should go directly to the literature. We are very fortunate to practice in a time where a search of the peer-reviewed literature is only a few mouse clicks away. It was not so very long ago when a literature search involved the assistance of a medical librarian. Often it would take days or weeks to get copies of the requested journal articles.
I have had a handful of patients with severe malabsorption who failed to respond to even extremely high-dose oral therapy (400 mcg to 500 mcg levothyroxine per day or more). Despite that, many continued to have elevated TSH with low serum T4 and T3. Although IV thyroxine is available for inpatients, it is not a practical long-term solution for an outpatient.
We attempt to overcome severe malabsorption by giving very high doses of levothyroxine (T4). Sometimes we even try adding liothyronine (T3) because it possibly may be absorbed more rapidly than T4. But even then, there are some patients who fail to respond. In such situations, non-compliance is a possibility and must not be overlooked. However, we do need to be cautious to avoid blaming our patients for lack of response when there are other reasons.
In patients with malabsorption who have failed all other treatment options, intramuscular thyroxine therapy could be extremely helpful if it were available. However, I could find only limited information about such therapy in the literature.
Readers: Do any of you have knowledge about intramuscular thyroxine therapy? If you have used it in you patients, what was your experience? What was the dose and how often was it given?
For more information:
Hays, M. Parenteral Thyroxine Administration. Thyroid. February 2007: 127-129.