Endocrine Abstracts

Fifty postmenopausal hypothyroid women (age 71.7±5.1 year) had been under replacement L-T4 therapy for 4.4±2.0 years before adding calcium carbonate (CC) (taken 1–2 h after L-T4). CC and tablet L-T4 were taken for the subsequent 2.3±1.1 years. Because serum TSH increased compared to L-T4 taken alone (3.33±1.0 vs 2.0±0.5 mU/l (baseline), P<0.001), with 9/50 having TSH values >4.12 mU/l, we instructed all 50 women to postpone CC after 6–8 h after L-T4 ingestion. This delay was unsatisfactory in the 9 women (2.88±0.37 mU/l vs 4.91±0.96 (delay of 1–2 h, P<0.001) and vs 2.19±0.45 mU/l (baseline, P<0.01), but it was satisfactory in the remaining 41 women (2.0±0.41 mUl vs 2.98±0.51 (delay of 1–2 h, P<0.001) and vs 1.90±0.40 mU/l (baseline, not significant)). Because of the relationship between TSH with blood pressure (BP), total cholesterolemia (CHOL) and fasting glycemia (FG), changes in these indices were evaluated from baseline through postponement of CC at 6–8 h after tablet L-T4. All indices worsened when CC was taken 1–2 h after L-T4 but decreased significantly when CC was taken 6–8 h after L-T4. However, these last values were greater than baseline, with FG significantly greater both in the 9 and 41 women. To assess whether TSH, CHOL, FG, SBP and DBP would decrease further under novel L-T4 formulations, we proposed to switch from tablet to the preferred formulation (liquid solution or softgel capsule) while maintaining the same daily dose of L-T4, timing from breakfast and 6–8 h delay from CC. Sixteen women (group 1) accepted (1/9 and 15/41; 9/16, liquid solution, and 7/16, capsule) while 34 women remained on tablet L-T4 and CC 6–8 h later (group 2). After 3 months, in group 1, TSH fell (1.23±0.49 vs 1.80±0.37, P<0.01), CHOL decreased borderline significantly (163±13 vs 171±13 mg/dl) and FG significantly (80.7±7.9 vs 83.4±6.3 mg/dl, P<0.05); SBP and DBP remained unchanged. In contrast, in group 2, TSH (2.43±0.89 vs 2.33±0.52) insignificantly increased, and all other indices increased too, DBP borderline significantly (69.7±9.0 vs 66.3±6.5 mmHg) and FG significantly (93.2±14.8 vs 89.5±14.5 mg/dl, P<0.01). Postponing the ingestion of CC by 6-8h after tablet L-T4 is not sufficient to ensure optimal levels of TSH and TSH-sensitive indices. In contrast, this goal can be achieved by either novel formulation of L-T4.