THYROID HORMONES IN NON-INSULIN-DEPENDENT DIABETES BEFORE AND AFTER THERAPY

Area of Science:

• Endocrinology
• Metabolic Disorders
• Thyroid Function

Background:

• Non-insulin-dependent diabetes mellitus (NIDDM) is a complex metabolic disorder.
• Secondary failure to oral hypoglycemic agents is common in NIDDM patients.
• Thyroid hormone status can be affected by metabolic control.

Purpose of the Study:

• To investigate thyroid hormone abnormalities in NIDDM patients with secondary failure to oral hypoglycemic drugs.
• To evaluate the effect of insulin therapy on thyroid hormone levels in these patients.
• To assess pituitary thyrotroph function in uncontrolled and controlled NIDDM.

Main Methods:

• Studied 20 NIDDM patients (15 male, 5 female) with secondary drug failure.
• Measured blood glucose, glycosylated hemoglobin (GHb%), serum tri-iodothyronine (T3), thyroxine (T4), reverse tri-iodothyronine (rT3), and thyrotropin (TSH) before and after insulin therapy.
• Assessed TSH response to thyrotropin-releasing hormone (TRH) before and after glycemic control.

Main Results:

• Insulin therapy significantly reduced fasting and post-prandial blood glucose and GHb% (p < 0.005 and p < 0.05, respectively).
• Serum T3 levels were significantly lower in uncontrolled NIDDM patients and rose significantly after insulin therapy (p < 0.05).
• Serum T4 levels did not change significantly, while rT3 levels decreased after therapy. TSH and TRH-TSH response remained unchanged.

Conclusions:

• Peripheral thyroid hormone changes (low T3, high rT3, normal/low T4) are characteristic of uncontrolled NIDDM.
• Pituitary thyrotroph function is not significantly affected in NIDDM patients with ideal body weight, even in the uncontrolled state.
• Intensive insulin therapy can normalize peripheral thyroid hormone abnormalities in NIDDM.