Summary
Turnover tracer studies of T4 and T3 using the single injection, noncompartmental approach were performed in 6 hypermetabolic patients with haematological disorders (HHD) (basal metabolic rate (BMR): median 141%, range 122-166%), in 10 controls with stable, nonthyroidal illness (NTIC), and in 14 healthy controls (HC).
The main finding was an increase of approximately 30% of the production rate (PR) of both T4 and T3 in patients with HHD. Median PR of T4 was 134 nmol/day × 70kg in HHD, compared to 78 nmol/day × 70 kg in NTIC (P < 0.05) and 98 nmol/day × 70 kg in HC (p < 0.1), whereas median PR of T3 was 40.3 nmol/day × 70 kg in HHD, compared to 25.6 nmol/day × 70 kg in NTIC (P < 0.01) and 31.1 nmol/day × 70kg in HC(P < 0.1). An increase of similar magnitude was found for the apparent distribution volume and the pool size of both T4 and T3. In contrast, the mean transit times of the hormones were similar in the 3 groups. Patients with HHD had normal levels of basal serum TSH as well as of the TSH response to TRH. Only PR of T3 correlated to the BMR (R = 1.00, P < 0.02).
The data are compatible with an increased consumption of thyroid hormones by malignant haematologic cells, and the increase of BMR seems to be dependent on the production of T3.
Key-Words
T4
- T3
- Production Rate - Hypermetabolism - Haematological Disorders
