Triiodothyronine suppresses humoral immunity but not T-cell-mediated immune response in incubating female eiders (Somateria mollissima)

Immunity is believed to share limited resources with other physiological functions and this may partly account for the fitness costs of reproduction. Previous studies have shown that the acquired immunity of female common eiders (Somateria mollissima) is suppressed during the incubation fast. To save energy, triiodothyronine (T3) is adaptively decreased during fasting in most bird species, despite T3 levels are maintained throughout incubation in female eiders. However, the relationship between thyroid hormones and the immune system is not fully understood. The current study aimed to determine the endocrine mechanisms that underlie immunosuppression in incubating female eiders. ...