Hypothyroidism: A Reminder of the Often Forgotten Intricacies

Very little has changed with regard to the treatment of primary hypothyroidism since the introduction of levothyroxine sixty years ago. It is safe, effective and relatively cheap. For all these reasons, both condition and treatment often drop to the bottom of priority lists in terms of patient and medication review, which, much of the time, is reasonable and justified. However, when a drug acquires this ‘reputation’, there is a danger that important details become slowly diluted until in some instances they are forgotten about altogether. The fact is, there are some quite unique and critical points to levothyroxine treatment, which, if ignored, can result in suboptimal therapy and patient harm. Indeed research shows a third of patients are inadequately treated. 1 Considering the burden of hypothyroidism with respect to associated comorbidities such as diabetes and cardiovascular disease, decreased quality of life and economic impact of same, a third of patients inadequately treated is significant. This article aims to highlight the salient points associated with hypothyroidism and levothyroxine therapy.

The thyroid produces two major hormones; Thyroxine (T4) and triiodothyronine (T3) in approximately a 4:1 ratio with most T4 subsequently being converted to T3 in the blood. Release of these hormones is triggered by Thyroid Stimulating Hormone (TSH) from the pituitary gland, which itself is triggered by Thyrotropin Releasing Hormone (TRH) from the hypothalamus. Initial diagnosis of hypothyroidism is usually on the basis of an elevated TSH level combined with a low free thyroxine level (FT4).