The impact of severe nephrotic syndrome on thyroid function, nutrition and coagulation

Background Nephrotic syndrome (NS) is characterized by urinary loss of proteins, including hormones and their carrier proteins, potentially resulting in endocrine disorders. This study aimed to assess thyroid dysfunction frequency and potential implications in NS. Methods In this case-control study, patients with severe NS (serum albumin ≤ 2.5 g/dL) and controls without proteinuria were evaluated for thyroid, hemostatic, and nutritional parameters, including body composition. Results Forty-two nephrotic and 40 non-proteinuric patients were enrolled. The NS group showed higher thyroid-stimulating hormone and lower free hormones, corresponding to a higher frequency of both euthyroid sick syndrome (ESS; 36% vs 5%; OR = 10.6, 95%CI: 2.2–50.0), and hypothyroidism (31% vs 5%; OR = 8.5, 95%CI: 1.8–40.7) compared to the control group. Levothyroxine supplementation was required for 11 NS patients (26% of the NS group). In addition, in comparison to the control individuals, NS patients exhibited lower lean tissue mass and a trend towards hypercoagulability, which was evidenced by higher levels of most coagulation factors and fibrinolysis inhibitors, and reduced endogenous anticoagulants activities. Furthermore, NS patients with ESS presented with a 10.4 kg (95% CI: −18.68 to −2.12) lower lean tissue mass. Those with hypothyroidism had a significantly reduced activity of coagulation factor X (by −30%, 95%CI: −47 to −13) and protein S (by −27%, 95%CI: −41 to −13) compared to euthyroid NS individuals. Conclusions Thyroid dysfunction is common in severe NS, often necessitating levothyroxine supplementation, which supports routine thyroid workup. A potential link between thyroid, nutritional, and coagulation disorders in NS requires further investigation.