The aim of this study was to assess the influence of low-level laser therapy (LLLT) or polarized light (PL) in cutaneous
wound healing of hypothyroid rats at dosages of 20 or 40J/cm2. Bioestimulatory effects of Laser radiation and Polarized
light are recognized alternative therapies to improve healing on systemic disease patients, but their usefulness in the
improvement of hypothyroidism healing impairment is uncertain till date. Forty Wistar rats were used in this study.
Hypothyroidism was propylthiouracil- induced. Standard excisional cutaneous wounds were created without suturing and
LLLT (λ660nm, 30mW, φ 3mm) or PL (λ 400-2000nm, 40mW, φ 10mm) was applied every 48 hours up to seven days
on experimental groups. The rats were killed on the eighth day when wound contraction was assessed. The healing
features were evaluated by light microscopy (H/E and Sirius Red). The cutaneous wounds of hypothyroid rats showed
delayed healing process characterized by reduced thickness of epithelial layers, incipient formation of disorganized
collagen fibers and wound contraction to a lesser extent (FISHER, p=0.0276), when compared to the euthyroid group.
The use of both the Laser and Polarized Light on hypothyroid rats increased the amount of fibroblasts and the thickness
of collagen fibers, especially on the L 20J/cm2 group. Euthyroid rats have still demonstrated more regular collagen
fibers pattern than hypothyroid rats. It was therefore concluded that hypothyroidism delays wound healing and both
Laser photobiomodulation and Polarized Light at 20j/cm2 dosages had improved the healing process in hypothyroid rats.