Dr. Gary Pepper, who uses Armour in his patients who don't get along with T4 mono-therapy, presented at the recent ATA meeting this month. This is the abstract. By the way his patients on Armour, some of whom are advanced in years, do just fine, in case anyone was curious. What a surprise, 120 years of usage of NDT and still no reports of people dropping like flies from taking it. PR
G.M. Pepper1,2, P. Casanova1,2, K. Reynolds1,2
1University of Miami, Jupiter, FL
2Palm Beach Diabetes and Endocrinology, Jupiter, FL
Individuals with hypothyroidism may report persistent symptoms typical of thyroid hormone deficiency despite peripheral thyroid hormone levels in the normal range. One possible explanation proposed by Bianco et al is tissue specific variation in deiodinase conversion of levothyroxine (LT4) to triiodothyronine (T3) resulting in normalization of TSH levels before peripheral T3 levels are optimized. To investigate this we analyzed thyroid functions of hypothyroid patients with satisfactory and unsatisfactory clinical responses to LT4. Those in the latter group also achieved substantial clinical benefit after conversion to a product containing LT4 and T3 (Armour Thyroid).
We retrospectively reviewed T4, T3 and TSH levels in three groups of adults; 1. Good responders (GR); clinically euthyroid on LT4, N=67. 2. Poor responders (PR), persistent symptoms of hypothyroidism on LT4 who reported substantial improvement after conversion to Armour Thyroid, N=57. 3. Normal controls (NC), N=54
Tukey-Kramer's test indicated mean T4/T3 ratio significantly greater in GR (10.3±1.9) than PR (9.3±2.5) and NC (8.5±2.0); p<0.01. T3 levels were significantly higher in PR (1.0±0.25 ng/dl) than GR (0.87±0.18 ng/dl) and NC (0.9±0.17 ng/dl), p<0.01. LT4 levels were similar in PR (9.0±1.8 ng/dl) and GR (8.8±1.6 ng/dl) but both significantly higher than NC, p<0.01. TSH levels were significantly lower in PR (1.09±1.16 μIU/mL) than NC (1.52±0.75 μIU/mL), P<0.01 but no different than GR (1.23±0.74 μIU/mL)
Peripheral T3 levels in PR would be expected to be lower than GR if tissue specific variation in deiodinase activity was the explanation of poor clinical response to LT4 replacement in primary hypothyroidism. Here, T3 levels in PR were higher than GR while TSH levels were similar. An alternate explanation for these findings would be relative T3 resistance in PR.