Effect of Liothyronine Treatment on Dermal Temperature and Activation of Brown Adipose Tissue in Female Hypothyroid Patients: A Randomized Crossover Study

Temperature Differences Between Controlled Primary Hypothyroidism and Healthy Patients: An Exploratory Study

Introduction

Hypothyroidism is conventionally treated with replacement therapy through levothyroxine (LT4). Despite the improvement in symptoms, cold intolerance persists in some patients. The present study aims to determine whether there is a difference in temperature perception and skin temperature between patients with primary controlled hypothyroidism (PCH) and a group of healthy controls matched for body mass index and age. Secondarily we aimed to determine difference in quality of life.

Methodology

Skin temperature measurements were performed in both groups, both in the central and peripheral regions of the body. In addition, subjects were asked about their perception of temperature in a temperature-controlled room; anthropometric measurements were taken, their quality of life was assessed using the ThyPRO-39, and a thyroid hormone profile was performed.

Results

Eleven patients in the PCH group and 30 patients in the control group were studied. It was found that the group with PCH presented a significantly lower palmar temperature than the control group [mean (SD) of 32.05 (1.79) vs 33.10 (1.30) oC, P = .046]. A mediation model showed a direct effect. Temperature perception was equal between groups. The median (interquartile range) of ThyPRO was 8 (5.2) points in the control group vs 21.8 (13.5) in the group of controlled hypothyroidism, P < .001.

Discussion

These results suggest that, despite LT4 treatment, patients continue to present abnormalities in thermogenesis-related thermogenesis, and this may be due to a lack of hormonal adaptation to environmental changes and physiological demands, leading to lower body temperatures and increased sensitivity to cold.

Pharmacological modulation of adaptive thermogenesis: new clues for obesity management?

BACKGROUND

Adaptive thermogenesis represents the main mechanism through which the body generates heat in response to external stimuli, a phenomenon that includes shivering and non-shivering thermogenesis. The non-shivering thermogenesis is mainly exploited by adipose tissue characterized by a brown aspect, which specializes in energy dissipation. A decreased amount of brown adipose tissue has been observed in ageing and chronic illnesses such as obesity, a worldwide health problem characterized by dysfunctional adipose tissue expansion and associated cardiometabolic complications. In the last decades, the discovery of a trans-differentiation mechanism ("browning") within white adipose tissue depots, leading to the generation of brown-like cells, allowed to explore new natural and synthetic compounds able to favour this process and thus enhance thermogenesis with the aim of counteracting obesity. Based on recent findings, brown adipose tissue-activating agents could represent another option in addition to appetite inhibitors and inhibitors of nutrient absorption for obesity treatment.

PURPOSE

This review investigates the main molecules involved in the physiological (e.g. incretin hormones) and pharmacological (e.g. β3-adrenergic receptors agonists, thyroid receptor agonists, farnesoid X receptor agonists, glucagon-like peptide-1, and glucagon receptor agonists) modulation of adaptive thermogenesis and the signalling mechanisms involved.

Thyroid Signaling Biomarkers in Female Symptomatic Hypothyroid Patients on Liothyronine versus Levothyroxine Monotherapy: A Randomized Crossover Trial

Background

Levels of thyroid-stimulating hormone (TSH) are believed to reflect degree of disease in patients with hypothyroidism, and normalization of levels is the treatment goal. However, despite adequate levels of TSH after starting levothyroxine (LT4) therapy, 5–10% of hypothyroid patients complain of persisting symptoms with a significant negative impact on quality of life. This indicates that TSH is not an optimal indicator of intracellular thyroid hormone effects in all patients. Our aim was to investigate different effects of LT3 and LT4 monotherapy on other biomarkers of the thyroid signaling pathway, in addition to adverse effects, in patients with residual hypothyroid symptoms.

Methods

Fifty-nine female hypothyroid patients, with residual symptoms on LT4 monotherapy or LT4/liothyronine (LT3) combination therapy, were randomly assigned in a non-blinded crossover study and received LT4 or LT3 monotherapy for 12 weeks each. Measurements, including serum analysis of a number of biochemical and hormonal parameters, were obtained at the baseline visit and after both treatment periods.

Results

Free thyroxine (FT4) was higher in the LT4 group, while free triiodothyronine (FT3) was higher in the LT3 group. The levels of reverse triiodothyronine (rT3) decreased after LT3 treatment compared with LT4 treatment. Both low-density lipoprotein (LDL) and total cholesterol levels were reduced, while sex hormone-binding globulin (SHBG) increased after LT3 treatment compared with LT4 treatment. The median TSH levels for both treatment groups were within the reference range, however, lower in the LT4 group than in the LT3 group. We did not find any differences in pro-B-type natriuretic peptide (NT pro-BNP), handgrip strength, bone turnover markers, or adverse events between the two treatment groups.

Conclusion

We have demonstrated that FT4, FT3, rT3, cholesterol, and SHBG show significantly different values on LT4 treatment compared with LT3 treatment in women with hypothyroidism and residual symptoms despite normal TSH levels. No differences in general or bone-specific adverse effects were demonstrated. This trial is registered with NCT03627611 in May 2018.

Effect of Liothyronine Treatment on Quality of Life in Female Hypothyroid Patients With Residual Symptoms on Levothyroxine Therapy: A Randomized Crossover Study

OBJECTIVE

The effects of levothyroxine (LT4)/liothyronine (LT3) combination therapy on quality of life (QoL) in hypothyroid patients former on LT4 monotherapy have been disappointing. We therefore wanted to test the effects of LT3 monotherapy on QoL in hypothyroid patients with residual symptoms despite thyroid stimulating hormone (TSH) values within the reference range.

DESIGN

Female hypothyroid patients with residual symptoms on LT4 monotherapy or combination LT4/LT3 therapy received LT3 and LT4 monotherapy, respectively for 12 weeks in a non-blinded randomized crossover study.

METHODS

Fifty-nine patients aged 18-65 years were included. QoL was assessed using one disease-specific questionnaire (ThyPRO) and two generic questionnaires (Fatigue Questionnaire and SF-36) at baseline and at the end of the two treatment periods. Clinical indices of cardiovascular health (resting heart rate and blood pressure), as well as thyroid tests, were assessed at baseline and at the end of the two treatment periods.

RESULTS

After 12 weeks of LT3 treatment, 12 of the 13 domains of the ThyPRO questionnaire (physical, mental and social domains) showed significant improvements. The most pronounced improvements were less tiredness (mean -21 ± 26; P<0.0001) and cognitive complaints (mean -20 ± 20; P<0.0001). LT4 monotherapy exerted minor effects on two domains only (cognitive complaints and impaired daily life). All three dimensions' scores in the Fatigue Questionnaire (physical, mental and total fatigue) improved after LT3 treatment compared to baseline (P<0.001), and in the SF-36 questionnaire 7 of 8 scales showed significantly better scores after LT3 treatment compared to baseline. There were no differences in blood pressure or resting heart rate between the two treatment groups. TSH in patients on LT3 was slightly higher (median 1.33 mU/L (interquartile range (IQR) 0.47-2.26)) than in patients on LT4 (median 0.61 mU/L (IQR 0.25-1.20; P<0.018). Five patients on LT3 dropped out of the study due to subjectively reported side effects, compared to only one on LT4.

CONCLUSIONS

LT3 treatment improved QoL in women with residual hypothyroid symptoms on LT4 monotherapy or LT4/LT3 combination therapy. Short-term LT3 treatment did not induce biochemical or clinical hyperthyroidism, and no cardiovascular adverse effects were recorded. Further studies are needed to assess the long-term safety and efficacy of LT3 monotherapy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT03627611.