The kidney is responsible for the excretion of thyroid hormones. The present retrospective study was conducted to find out the association of serum thyroid stimulating hormone (TSH) and free thyroxine (FT4) with urinary albumin excretion in euthyroid subjects with type 2 diabetes mellitus (T2DM) in Saudi community based hospital.
We analyzed retrospectively 939 participants whom are between the age 20 to 96 years. All patients were from the population of the Primary health centre at King Fahad Armed Forces Hospital, Jeddah, Saudi Arabia. All data were collected on the basis of a review of electronic medical data. Participants were defined as having T2DM according to self-report, clinical reports, use of antidiabetic agents and HbA1c (≥ 6.5). HbA1c was expressed as percentage. High performance liquid chromatography was used. Serum FT4 were estimated by radioimmunoassay and Serum TSH was estimated by Immunoradiometric assay. All patients in the present study fulfilled the revised National Kidney Foundation criteria for the diagnosis of albuminuria. The urine albumin to creatinine ratio (ACR) was used as the index of urinary albumin excretion. A urine sample was collected during the first morning voiding. Conventionally, subjects with ACR < 30 mg/g were defined as having normal albuminuria (NA). ACR between 30-299 mg/g is called moderately increased albuminuria. Levels ≥ 300 mg/g are called severely increased albuminuria.
939 subjects with T2DM were included. There were 299 (31.8%) male and 640 (68.2%) were female with mean age 55.9 ± 12.5. The mean TSH and FT4 value were 1.9 ± 0.9 mIU/l and 15.8 ± 2.5 pmol/l respectively. Among cases of T2DM and albuminuria, there were 608 (64.7%) with NA, 262 (27.9%) with moderately increased albuminuria and 70 (7.4%) with severly increased albuminuria. Patients with severely increased albuminuria were significantly older than patients with NA and moderately increased albuminuria, 58.9 ± 9.9 vs. 55.1 ± 12.4 and 56.9 ± 13.1 respectively, p = 0.02. Frequency of female patients were higher across all albuminuria grades, p = 0.001. Patients with severely increased albuminuria were significantly have higher TSH than patients with NA and moderately increased albuminuria, 2.1 ± 0.9 vs. 1.8 ± 0.9 and 1.9 ± 0.9 respectively, p = 0.02. Patients with severely increased albuminuria were significantly have lower FT4 than patients with NA and moderately increased albuminuria, 15.3 ± 1.9 vs. 16.1 ± 2.5 and 15.4 ± 2.6 respectively, p = 0.045. Patients with severely increased albuminuria have higher TSH than patients with NA and moderately increased albuminuria across all age groups. Patients with severely increased albuminuria have lower FT4 than patients with NA and moderately increased albuminuria across all age groups.
We conclude that despite the limitations of this hospital-based retrospective study, high TSH and low FT4 levels are highly prevalent in cohort of Saudis with albuminuria and T2DM. The majority of our patients in our finding were predominantly females. These two observations remain to be validated by population-based studies. In the absence of registry data, larger cooperative studies involving diverse population samples from multiple centers could help to provide further information on the true thyroid hormone abnormalities.