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Brown adipose tissue thermogenic response in children with hypothyroidism
Author(s) -
Law James,
Robinson Lindsay,
Astle Valerie,
Finn Ellie,
Denvir Louise,
Randell Tabitha,
Marshall Andrew,
Sacks Harold,
Symonds Michael,
Budge Helen
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.886.9
Subject(s) - brown adipose tissue , thermogenesis , medicine , endocrinology , triiodothyronine , iodothyronine deiodinase , shivering , population , thyroid , thermoregulation , adipose tissue , deiodinase , physiology , environmental health
Brown adipose tissue (BAT) is a key component of non‐shivering thermogenesis. It is primarily activated by the sympathetic nervous system, but thyroid hormones can also modulate its activation. Type II iodothyronine deiodinase within brown adipocytes converts thyroxine to the active form, triiodothyronine, resulting in increased uncoupling protein 1 expression. Animal models of hypothyroidism show a marked reduction in both BAT function and the ability to respond to cold stress via non‐shivering thermogenesis. In humans, functional BAT has been shown in patients with hypothyroidism, but whether thyroxine replacement increases or decreases BAT activity is unclear. BAT is more active in the paediatric population but the effect of hypothyroidism has not been studied. We therefore utilised infrared thermography to ascertain the effect of thyroid status on BAT activity in children. Forty‐two paediatric patients (median age 12.4 years, IQR 9.8–14.1 years) were entered into the study with National Research Ethics Service approval and following informed consent, of who 21 were diagnosed with hypothyroidism and 21 were healthy controls. Children were imaged in an upright position and a time series of thermal images acquired prior to and following introduction of a cold water stimulus (median temperature 18.5°C, IQR 17.9°C −18.8°C) to an upper limb. BAT temperature was defined as the median of the warmest 10% of pixels within the supraclavicular region. Primary outcome was the change in temperature of the region of interest from baseline after 5 minutes stimulation (ΔT). Children with hypothyroidism had a significantly lower baseline BAT temperature ( Figure 1a). However, there was no difference between groups in baseline temperature when expressed relative to a reference point on the sternum ( Figure 1b). Although there were no absolute or relative differences in ΔT between groups (p=0.33, p=0.75 respectively), children with hypothyroidism had a delayed BAT response ( Figure 2) and, on adjustment for age and weight SDS, children with hypothyroidism had a significantly greater relative ΔT (GLM, estimate = 0.12 p=0.026). Children with hypothyroidism show a reduced BAT temperature and delayed response to cool stimulus, but retain the magnitude of their thermogenic response. Support or Funding Information Funding for this project has been received from the Nottingham University Hospitals Charity (Nottingham, UK).Baseline right supraclavicular temperature by group (a) absolute SCR temperature (Control = 35.40°C, Hypothyroid=34.95°C, p=0.046) and (b) SCR temperature relative to a reference point on the sternum (p = 0.869) (mean ± SEM; closed circles ‐ hypothyroid; open circles ‐ control).Change in right supraclavicular temperature by group prior to, and during, stimulation a) absolute SCR temperature and b) SCR temperature relative to a reference point on the sternum (mean ± SEM; closed circles ‐ hypothyroid; open circles ‐ control; ‐ ‐ introduction of stimulus at time = 0 minutes).