Page 20 - HKSEMR2020 Programme book

Oral Presentation (Clinical) Abstracts

Evaluation of the optimal thyroxine levels for thyroid hormone

replacement in patients with central hypothyroidism

Hay Man So, Ka Fai Lee, Maria Wai Han Mak
Kwong Wah Hospital

Introduction / Background / Objectives:
Central hypothyroidism results from pituitary or hypothalamic Results / Outcomes:
dysfunction. The evaluation of the adequacy of thyroxine We demonstrated that raising the fT4 target from lower to upper
replacement is difficult, due to the loss of thyrotropin (TSH) as an tertile within the normal reference range resulted in a significant
accurate feedback marker. The current study was undertaken to decrease in body mass index (27.1±6.0 vs 25.7±5.6 kg/m , P <
2
determine the optimal free T4 (fT4) level for thyroxine replacement 0.01), waist circumference (89.5±12.7 vs 86.4±12.1 cm, p < 0.01),
with a favourable metabolic and clinical profile in central diastolic blood pressure (79.1±12.9 vs 74.5±12.9 mmHg, p < 0.05)
hypothyroidism.
and low density lipoprotein cholesterol (3.94±0.88 vs 2.90±0.71
mmol/L, p < 0.01). The occurrence of metabolic syndrome (48.2%
vs 29.0%, p < 0.05) was significantly reduced with increasing
Methods:
fT4 from middle to upper tertile, without a significant effect on
This was a single centre, prospective open-label crossover-like glycaemic indexes.
trial of 51 patients (mean age 56±12.9 years, 27 males) with
hypopituitarism with multiple hormonal deficiencies including
central hypothyroidism. Dosage of levothyroxine (L-T4) was titrated Conclusion:
to a targeted lower, middle and upper fT4 tertile and maintained In this study, we demonstrated that raising the fT4 target to the
for 24 weeks before assessment. Anthropometric and physiological upper tertile of normal resulted in a favourable improvement in
measurements, metabolic and peripheral tissue markers, and various metabolic indexes without a significant increase in adverse
cognitive and quality of life assessments were compared before effects over a period of 48 weeks.
and after each fT4 tertile change. This was followed by another 24-
week cycle of L-T4 dosage adjustment to achieve fT4 in another
tertile, with the same assessment as above.

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