Endocrine Abstracts

Once daily Thyroxine is the treatment of choice for hypothyroidism. The dose of Thyroxine needed varies with a mean of 1.6 mcg/kg bodyweight a day. The most common cause for requiring larger doses is non-compliance although other causes such as malabsorption and drugs should be excluded. In this abstract we describe two patients with hypothyroidism that required large doses of thyroxine secondary to poor compliance in which supervised once weekly thyroxine therapy was successful. Patient-1: A 47-year-old female was referred with uncontrolled primary hypothyroidism that was diagnosed in 2001. Thyroxine dose was gradually increased, by her general practitioner, to 375 micrograms/day at referral. She wasn’t taking any medications that interfere with thyroxine absorption and denied non-compliance. Initial investigations were unremarkable and malabsorption was excluded. Thyroid function tests (TFTs) showed F-T4 of 10.9 pmol/l (10.0–25.0) and a TSH of 32.5 mu/l (0.40–4.00). Over the last 3 years, TSH levels were consistently elevated (20.20 to 36.10). TSH remained elevated despite increasing thyroxine dose to 400mcg daily. Six weeks treatment with supervised once-weekly 1 mg of thyroxine resulted in improvement in TFTs, F-T4 28.5 pmol/l and a TSH of 0.05 mu/l. Therefore her weekly dose was reduced to 750 mcg. Patient-2: A 48-year-old female recently diagnosed with primary hypothyroidism (F-T4 5.6 and TSH >75). TSH remained persistently high despite increasing dose of Thyroxine to 200 micrograms. She denied non-compliance. Malabsorption syndromes were excluded. She wasn’t on any medications that interfere with thyroxine absorption. Supervised once-weekly thyroxine replacement 800 mcg for 4 weeks resulted in TSH falling to 1.93 mu/l.

Conclusions

These cases illustrate that supervised once weekly thyroxine treatment can be used successfully in non-compliant patients with hypothyroidism. Endocrinologist treating non-compliant patients with hypothyroidism should be aware of this possible approach to treatment.