Thyroid function in patients with proteinuria and normal or increased serum creatinine concentration.

Area of Science:

• Nephrology
• Endocrinology
• Clinical Chemistry

Background:

• Proteinuria is a common finding in kidney disease.
• Thyroid hormone metabolism can be altered in patients with renal impairment.
• Urinary loss of thyroid hormones has not been extensively studied in relation to proteinuria.

Purpose of the Study:

• To investigate thyroid function in patients with proteinuria.
• To compare urinary thyroid hormone excretion in patients with normal versus elevated creatinine levels.
• To assess the impact of urinary hormone loss on serum thyroid hormone concentrations.

Main Methods:

• Studied 13 patients with proteinuria and normal serum creatinine (Group 1) and 15 with proteinuria and elevated creatinine (Group 2).
• Measured daily urinary T4 and T3 excretion.
• Assessed serum concentrations of T4, T3, FT4, FT3, TBG, TBPA, rT3, and TSH.

Main Results:

• Urinary T4 and T3 excretion were significantly higher in Group 1 than Group 2, correlating with protein loss.
• No patient developed hypothyroidism despite substantial hormone loss.
• Serum thyroid hormone levels were generally within normal ranges, but urinary loss influenced these values, with low rT3 observed in some patients.
• Basal TSH levels were similar to normal individuals.

Conclusions:

• Proteinuria leads to significant urinary loss of thyroid hormones (T4 and T3).
• This loss, while not causing hypothyroidism, impacts serum thyroid hormone levels, particularly reverse T3 (rT3).
• Assessing thyroid function in patients with proteinuria and renal failure is complex due to multiple influencing factors.