Renal dysfunction caused by severe hypothyroidism diagnosed by renal biopsy: a case report

Abstract

There is a close relationship between thyroid dysfunction and renal dysfunction. However, thyroid dysfunction can unfortunately result in inaccurate measurements of serum creatinine and cystatin C levels. The chronic decrease in cardiac output due to hypothyroidism can reduce renal plasma flow (RPF) resulting in renal dysfunction. We report the case of a 36-year-old male in whom renal dysfunction detected during a company health check-up was found to be caused by severe hypothyroidism. His serum creatinine levels showed poor results, but serum cystatin C levels were within the normal range. The physician thus prioritized serum cystatin C for assessing the patient's renal function, and concluded that his renal function was normal. He subsequently visited our hospital, aged 36 years, for a comprehensive examination. His serum creatinine level was 1.88 mg/dL and his serum cystatin C level was 0.75 mg/dL, indicating an unusual discrepancy between the two measurements. The patient also presented with fatigue, suggesting hypothyroidism, and we therefore evaluated his thyroid function. His free thyroxine level was below the sensitivity of the assay, while his thyroid-stimulating hormone level was > 100 μIU/mL. A renal biopsy was performed to further explore the underlying cause of his renal dysfunction, which suggested that reduced RPF could be the leading cause of his renal ischemia, with no indications of chronic glomerulonephritis or other abnormalities. His hypothyroidism and renal function improved after thyroid hormone replacement therapy. Given the limited reports of renal biopsy tissue examination during the acute phase of hypothyroidism, the current case provides important information regarding the diagnosis of renal dysfunction in patients with hypothyroidism.

Keywords: Abnormal hemodynamic state; Cystatin C; Glomerular filtration rate; Hypothyroidism; Ischemic change; Renal biopsy; Renal plasma flow.

Fig. 1

US and CT findings. a US images of the thyroid show diffuse swelling and a hypoechoic thyroid. No blood flow signal enhancement was observed. b Hematological examination shows liver dysfunction, but liver CT shows no abnormalities in liver morphology. c US images of bilateral kidneys show no indications of kidney dysfunction. The patient’s kidneys show a normal morphology and no atrophy. US: ultrasound, CT: computed tomography

Fig. 2

Histological examination of renal biopsy specimens. Periodic acid-methenamine silver staining of renal biopsy tissue (× 400) shows no remarkable findings in most glomeruli (a), but wrinkling of the glomerular basement membrane and collapsed glomerular tufts in some glomeruli can be seen (b). Black, red, and blue windows in (b) represent magnified views of smaller same-colored windows in three locations in the glomerulus. Scale bar = 50 μm. c Masson trichrome staining of renal biopsy tissue (× 200) shows focal tubular atrophy and interstitial fibrosis accompanied by mononuclear cell infiltration. Scale bar = 100 μm. d Immunofluorescent images of frozen sections are negative for immunoglobulin and complement. e Electron microscopy shows intact glomeruli and no organic abnormalities

Fig. 3

The patient’s clinical course. Changes in the eGFR (eGFRcreat, green lines; eGFRcys, blue lines) and TSH levels (red lines) are shown. The box at the top of the table and the numbers within the box represent the dosage of levothyroxine. TSH: thyroid-stimulating hormone, eGFRcreat: estimated glomerular filtration rate creatinine, eGFRcys: estimated glomerular filtration rate cystatin C