Presence of brown adipose tissue in an adolescent with severe primary hypothyroidism

Abstract

Context: Brown adipose tissue (BAT) generates heat during adaptive thermogenesis in response to cold temperature. Thyroid hormone (TH) receptors, type 2 deiodinase, and TSH receptors are present on brown adipocytes, indicating that the thyroid axis regulates BAT. It is unknown whether absent TH in humans would down-regulate development of BAT and its thermogenic function.

Objective: The objective of the study was to examine BAT by magnetic resonance imaging (MRI) and infrared thermal imaging (IRT) in a pediatric patient with severe primary hypothyroidism before and after TH treatment.

Design/setting: This study was a case report with longitudinal follow-up in a tertiary center.

Main outcome measures: BAT fat fraction (FF) by MRI and skin temperature by IRT were measured.

Results: An 11.5-year-old female was severely hypothyroid (TSH, 989 μIU/mL; free T4, 0.10 ng/dL; low thyroglobulin, 3.0 ng/mL). Low MRI measures of FF (56.1% ± 3.7%) indicated that BAT was abundantly present in the supraclavicular fossa. IRT showed higher supraclavicular temperature (36.0°C ±0.16°C) than the suprasternal area (34.3°C ± 0.19°C). After 2 months of TH replacement, she was euthyroid (TSH, 4.3 μIU/mL; free T4, 1.49 ng/dL; T3, 102 ng/dL) at which time supraclavicular BAT decreased (increased FF 60.7% ± 3.8%). IRT showed a higher, more homogeneous skin temperature throughout the upper thorax (supraclavicular, 37.1°C ± 0.23°C; suprasternal, 36.4°C ± 0.13°C). The overall size of the supraclavicular fat depot decreased from 84.79 cm(3) to 41.21 cm(3).

Conclusions: These findings document the presence of BAT and thermogenesis in profound hypothyroidism and suggest a role for TSH and/or TRH as a potential regulator of BAT.

Figures

Figure 1.

MRI volume rendering (top row) and FF (bottom row, coronal views) images of an 11.5-year-old female with severe, acquired hypothyroidism at diagnosis (A) and after 2 months of thyroid hormone (LT4) replacement therapy at which time she was euthyroid (B). Volume rendering depicts supraclavicular fat pad in yellow (white arrows). These images show an overall decrease in the volume of the supraclavicular fat depot (white arrows; 84.79–41.21 cm3) and a concomitant increase in mean FF at this site (56.1% ± 3.7% to 60.7% ± 3.8%). Scale to the right represents the FF (percentage).

Figure 2.

Digital (top row) and thermal (bottom row) images of an 11.5-year-old female with severe, acquired hypothyroidism at diagnosis (A) showing a higher skin temperature in the supraclavicular area (circle; 36.0°C ± 0.16°C) than the suprasternal area (rectangle; 34.3°C ± 0.19°C). After 2 months of thyroid hormone (LT4) replacement therapy (B), infrared thermography reveals a higher, more homogenous skin temperature throughout the upper thorax (supraclavicular area, 37.1°C ± 0.23°C; suprasternal area, 36.4°C ± 0.13°C). Scale to the right represents the temperature (degrees Celsius).