Relation between serum thyroid hormone and 'nondipper' circadian blood pressure variability

Area of Science:

• Endocrinology
• Nephrology
• Cardiovascular Medicine

Background:

• Nondipper hypertension pathogenesis is unclear in patients without renal or endocrine issues.
• Overt hypothyroidism is linked to diastolic hypertension, but the role of thyroid hormones in nondipper hypertension is unknown.

Purpose of the Study:

• To investigate the association between thyroid-stimulating hormone (TSH), free T3 (FT3), and free T4 (FT4) levels and nondipper hypertension.
• To assess these hormones in patients with normal renal function and no overt thyroid disorders.

Main Methods:

• 131 subjects with GFR >60 ml/min and no history of thyroid disorders or medication were enrolled.
• 24-hour ambulatory blood pressure monitoring was performed.
• Serum TSH, FT3, and FT4 levels were analyzed.

Main Results:

• Nondipper patients (55%) had significantly lower FT3 levels (4.0 +/- 0.9 pmol/l) compared to dippers (4.5 +/- 0.6 pmol/l).
• Nondipper patients also had lower glomerular filtration rate (GFR) (80.5 +/- 12.2 ml/min) versus dippers (86.9 +/- 16.9 ml/min).
• Lower FT3 levels were identified as the only independent predictor of nondipper hypertension (p = 0.04).

Conclusions:

• Lower FT3 levels are independently associated with an increased risk of nondipper hypertension.
• The precise pathogenetic mechanisms require further investigation.
• This study highlights a potential link between thyroid hormone levels and hypertension patterns.