Lazy Adrenals in Severe Hypothyroidism - Myth or Mirage?

Abstract

Background: Clinical features of hypothyroidism and adrenal insufficiency (AI) often overlap. Objectives: To assess the morning serum cortisol levels of treatment-naïve patients with severe hypothyroidism. Methods: In this prospective, case-control study, treatment-naïve adults with severe hypothyroidism [thyroid-stimulating hormone (TSH) > 100 mIU/mL] were compared with age- and sex-matched euthyroid controls. Morning (08:00 AM) serum cortisol, TSH, triiodothyronine (T3), and thyroxine (T4) levels were measured. AI was defined clinically and biochemically as cortisol levels < 4 µg/dL. Correlation coefficients between T3, T4, and cortisol levels were calculated. Results: The case group (n = 71; women, 88.7%; mean age, 30.0 ± 9.0 years) had significantly lower serum cortisol levels than controls (n = 40; 8.6 ± 4.2 vs 16.0 ± 2.22 µg/dL; P < 0.0001). Six patients (8.5%) in the case group met criteria for AI. Patients with AI had significantly lower T3 and T4 levels than those without AI (P = 0.018 and P = 0.005, respectively). A negative correlation was observed between T3 and cortisol levels (r = -0.243, P = 0.041), while T4 showed no significant correlation (r = -0.103, P = 0.391). Conclusions: Treatment-naïve patients with severe hypothyroidism may exhibit biochemical evidence of AI. Routine screening for AI in these patients is recommended to avoid missed diagnoses and guide appropriate therapy.