ECE2006 Poster Presentations Thyroid (174 abstracts)
Changes in thyroxine requirement in the long-term follow-up of hypothyroid patients
AK Viswanath 1 , A Avenell 2 , S Philip 1 , S Acharya 1 , G MacLennan 2 , K Dalziel 3 , SA Copland 1 , JS Bevan 1 & P Abraham 1
1Thyroid clinic, Aberdeen Royal Infirmary, Aberdeen AB25 2ZN, United Kingdom; 2HSRU, University of Aberdeen, Aberdeen, United Kingdom; 3IM&T Department, Aberdeen Royal Infirmary, Aberdeen, United Kingdom.
Background and methodology: There are few data on changes in thyroxine requirement in the long-term follow-up of hypothyroid patients. We carried out a retrospective analysis to evaluate the long-term changes in thyroxine dose and its relationship with age, gender, thyroxine dose at registration and aetiology of hypothyroidism.
Results: We identified 5,029 patients from our hospital based thyroid register with a minimum of 4 years follow-up (88% female, 74% autoimmune hypothyroidism, and mean age at registration was 53 S.D. 15 years). The mean thyroxine dose at registration was 115.5 S.D. 38 mcg/day (median 100). Patients with autoimmune hypothyroidism were on smaller doses (111 mcg vs 127 mcg; P<0.01). After a median follow-up of 8.7 years there was an overall increment in thyroxine requirement (to a mean of 122 S.D. 44 mcg; median 125). This increment was seen predominantly in patients with autoimmune diseases who were perhaps on smaller thyroxine dose at registration or had progressive thyroid failure.
During follow-up thyroxine dose remained unchanged in 42% and a further 29% required only a minor adjustment in dose (25 mcg). Patients on thyroxine 100–150 mcg at registration were least likely to require a dose change. On regression analysis the final thyroxine dose was related to age, gender and thyroxine dose at registration. Women on an average required 12.8 mcg less thyroxine than men (95% CI 10.2 to15.5; P<0.001). As patients got older, thyroxine requirement fell by 0.73 mcg/year (95% CI 0.67 to 0.79; P<0.001). Thyroxine dose was unrelated to the aetiology of hypothyroidism.
Conclusions: During long-term follow-up, thyroxine dose remained unchanged in most patients who were registered on 100–150 mcg. Factors such as age, gender and thyroxine dose may be useful in identifying patients who can be monitored by longer intervals between thyroid function tests during routine surveillance.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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