Subclinical Primary Hypothyroidism May Be Common in Chronic Kidney Disease

Although this isn't new news, it's relatively recent and I just happened upon it. Since I'm having recurrent pyelonephritis, I was doing some research. This is not what I expected to find, but somehow my meanderings through the interconnected cyber-trails called the world wide web led me to this information on various sites. And as I looked more, I found this site with probably the most "free" information about it. If you have access to the full article, it's well worth the read.

Pertinent facts from the article:

• This study used results of serum creatinine, glucose, lipids, and thyroid function tests in a large database from the Clinical Chemistry Laboratory at the Verona University Hospital in Italy.
• From December 2005 to December 2007, a total of 3233 outpatient adults 18 years and older were consecutively referred by general practitioners for routine blood testing.
• All patients with low or high normal free thyroxine levels (n = 144) were excluded, leaving 3089 adult participants included in the final analysis.
• Mean age was 54.9 ± 16.2 years (range, 18 - 94 years); 78.4% were women.
• GFR was estimated from the abbreviated Modification of Diet in Renal Disease equation.
• The independent association between prevalent subclinical primary hypothyroidism and estimated GFR was determined with multivariable logistic regression.
• Subclinical primary hypothyroidism occurred in 293 (9.5%) of 3089 adult participants.
• Participants with subclinical primary hypothyroidism were likely to be older and had higher values of fasting plasma glucose, total cholesterol, and triglycerides, and lower estimated GFR levels vs those with no subclinical hypothyroidism.
• Estimated GFR was less than 60 mL/minute per 1.73 m² in 277 (9%) participants.
• Subclinical primary hypothyroidism became more prevalent with decreasing GFR.
• The prevalence of subclinical primary hypothyroidism was 7% at an estimated GFR of more than 90 mL/minute per 1.73 m² and 17.9% at an estimated GFR of less than 60 mL/minute per 1.73 m² (P < .0001 for trend).
• Odds of subclinical primary hypothyroidism were increased in participants with an estimated GFR of less than 60 mL/minute per 1.73 m² vs those with an estimated GFR of more than 60 mL/minute per 1.73 m² after adjustment for age; sex; and fasting plasma glucose, total cholesterol, and triglyceride concentrations.
• Throughout the normal and high TSH ranges, there was a significant inverse association between estimated GFR and TSH levels.
• Older age was also independently associated with prevalent subclinical hypothyroidism, but sex, fasting plasma glucose levels, and lipid levels were not.
• The investigators concluded that subclinical primary hypothyroidism is relatively prevalent (approximately 18%) among persons with CKD not requiring long-term dialysis and that it is independently associated with progressively lower estimated GFR in a large cohort of unselected outpatient adults.
• Limitations of the study include cross-sectional design, precluding determination of causal or temporal relationships; definition of kidney function based on estimated GFR; inability to identify nonthyroidal and thyroidal causes of subclinical hypothyroidism; possible misclassification resulting from use of automated databases; and lack of data on comorbid conditions and use of thyroid medications.

To read more: Subclinical Primary Hypothyroidism May Be Common in Chronic Kidney Disease