Endocrine Abstracts

We have studied 20 patients with autoimmune hypothyroidism on large doses of daily thyroxine that were referred to our departments with concerns regarding possible thyroxine malabsorption or compliance issues. Here we describe 3 patients seen in Oxford. One patient had coeliac disease. The other two patients had no history of malaborption and were coeliac antibody negative. None of the 3 patients were on medication which would interfere with thyroxine absorption. All were female with a mean age 44 (34–55).

Following consent the subjects attended on a weekly basis for supervised thyroxine administration. Each patient stopped their daily dose of thyroxine and received on average 12 mcg/kg per week as a starting dose. This was crushed and mixed with jam. An intravenous cannula was inserted and bloods for TSH and FT₄ were taken at time 0 and 120 minutes after ingestion.

In all three patients, a significant TSH response was demonstrated:

Patient 1 with coeliac disease had a TSH 109.57 mU/L (0.35–5.5) and FT₄ 3.7 pmol/L (11.5–22.7) prior to starting weekly thyroxine. The dose was gradually increased every 4 weeks to 25 mcg/kg and the TSH improved to 4.73 mU/L and a FT₄ 17 pmol/L after 16 weeks.

Patient 2 had a TSH of >150 mU/L and FT₄ <3 pmol/L. The dose was gradually increased every 4 weeks to 18 mcg/kg and the TSH reduced to 5.55 mU/L with a FT₄ of 11.6 pmol/L after 16 weeks.

Patient 3 had an initial TSH of 21.03 mU/L and T₄ 12.3 pmol/L. After 4 weeks on the starting dose of weekly thyroxine the TSH had reduced to 4.17 mU/L with a FT₄ of 16.6 pmol/L.

No adverse side effects were reported during the weekly administration.

We have shown that weekly thyroxine administration is safe and effective. Supervised thyroxine administration may be needed to ensure compliance. The TSH may take several weeks to fall into the normal range.