#1246 The impact of severe nephrotic syndrome on thyroid function

Abstract Background and Aims Nephrotic syndrome (NS) is a clinical condition characterized by massive urinary loss of proteins, mostly albumin, but also hormones and their carrier proteins among others. The most frequently reported hormonal complication is thyroid dysfunction. The study aimed to assess the frequency of thyroid dysfunction in NS and its association with carrier protein levels and indicators of disease severity. Method A case-control study was conducted involving patients with newly diagnosed or relapsed severe NS, defined as proteinuria 3.5 g/day and serum albumin ≤ 2.5 g/dL (NS group), and patients without proteinuria (control group). The evaluation included thyroid hormone profiles, serum levels of carrier proteins (prealbumin – PAB, and thyroid-binding globulin – TBG), and markers reflecting the course of NS. Results Forty-two nephrotic and 40 matched non-proteinuric patients were enrolled. The NS group comprised 67% males with a mean age of 49 years and an average proteinuria of 8.9 g/day (Table 1). The leading cause of NS was minimal change disease (22 patients), followed by membranous nephropathy (11 patients). The other causes included: amyloidosis (3 patients: AL – 2 cases, A – 1 case), focal segmental glomerulosclerosis (2 patients) and lupus nephritis (1 case). In 5 cases, no histological diagnosis was made. Thyroid dysfunction secondary to NS was observed in the majority of patients, occurring 18-times more frequently than in the control group (67% vs 10%, OR = 18, 95% CI: 5.3-60.7). Euthyroid sick syndrome was the most commonly seen in NS (15 cases, 36%), followed by overt (8 cases, 19%) and subclinical hypothyroidism (5 cases, 12%). According to the current guidelines, levothyroxine supplementation was required in 11 patients (26% of the NS group, 36% of those with thyroid dysfunction). Serum TSH correlated inversely with PAB (R = −0.63, p 0.001), and positively with TBG (R = 0.39, p = 0.010), while no relationships were found between carrier proteins and free hormones (fT3 or fT4). The only indicator of NS severity related to thyroid function was serum albumin. It correlated, however, only with TSH (R = −0.41, p = 0.007), not with free hormones. Additionally, neither histological type, nor clinical course of NS distinguished between euthyroidism, euthyroid sick syndrome, or hypothyroidism (Table 2). Conclusion Thyroid dysfunction is a common complication of severe NS. Although euthyroid sick syndrome predominates, the proportion of patients with hypothyroidism who may potentially require levothyroxine replacement therapy remains substantial.