Dear Editor,
Most of our patients with hypothyroidism are diagnosed early and most are satisfied with their treatment. Many of these will retain residual thyroid function for some time. A small proportion of patients on thyroid hormone replacement are distressed and unsatisfied. They represent possibly 5-10% of all hypothyroidism cases. They have diffuse symptoms including fatigue, brain fog, or more typical dysthyroid phenomena such as cold sensitivity, dry skin, or constipation. Most of this minority can be identified from their patterns of laboratory tests. Many have quite frequent blood tests on record, as repeated adjustments of thyroxine therapy are made. Often they show high normal levels of free T4, accompanied by low or subnormal TSH levels. A common clinical sign in this setting is delayed tendon reflexes. The knee and ankle jerks showed very slow relaxation (a typical sign of hypothyroidism). These patients have T4/T3 imbalance, due to a relative deficiency of deiodinase enzymes that convert T4 to T3 (a genetic trait). They will show free T3 levels towards the lower limit of the normal range and they will have a high T4 to T3 ratio (greater than 4.0). A total of 11 clinical trials have been conducted to clarify this issue. Only two trials showed a benefit of adding T3 (Tertroxin) to the T4 (Thyroxine) treatment. This lack of compelling evidence is explained by inappropriate selection criteria. All of the trials were conducted on unselected patients with various forms of hypothyroidism, and without specific symptoms. The proper trial should be confined to that subset of patients who have symptoms and signs to suggest T4/T3
imbalance. Identifying these patients is often gratifying, for most will respond dramatically to the addition of Tertroxin (T3) to the Thyroxine (T4) at a reduced dose. Tertroxin requires an Authority Prescription. To give an example:
An unhappy patient taking Thyroxine 150 μg daily will do very well on Thyroxine 100 μg daily with Tertroxin 10 μg twice daily added. Reflexes will also improve. This remains a controversial topic with endocrinologists, because of the lack of sufficient clinical trial evidence.
Dr Tim Welborn,
Endocrinologist and Clinical Professor of Medicine