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Nicotinic acid decreases serum thyroid hormone levels while maintaining a euthyroid state
K M Shakir1, S Kroll, B S Aprill
1Division of Endocrinology and Metabolism, National Naval Medical Center, Bethesda, Maryland 20889-5600, USA.
Mayo Clinic Proceedings
|June 1, 1995
Summary
Nicotinic acid treatment in hyperlipidemia patients significantly lowered thyroid hormone levels, including total thyroxine (T4) and triiodothyronine (T3), without causing hypothyroidism. These changes may involve a reduction in thyroxine-binding globulin.
Area of Science:
- Endocrinology
- Pharmacology
Background:
- Hyperlipidemia is a common condition requiring effective treatment.
- Thyroid hormone levels can be influenced by various medications.
- Nicotinic acid is used to manage hyperlipidemia.
Purpose of the Study:
- To investigate the impact of nicotinic acid on serum thyroid hormone levels.
- To assess thyroid function in patients with hyperlipidemia treated with nicotinic acid.
- To determine if nicotinic acid affects thyroid hormones in the absence of systemic illness or liver dysfunction.
Main Methods:
- A study involving five hyperlipidemia patients (1 female, 4 male, mean age 44.4 years).
- Measurement of serum lipids, thyroxine (T4), triiodothyronine (T3) resin uptake, T3, free T4, thyroid-stimulating hormone (TSH), and thyroxine-binding globulin (TBG).
- Measurements were taken before, during, and after nicotinic acid treatment (mean daily dose 2.6 g).
Main Results:
- Nicotinic acid effectively lowered serum lipid levels.
- Significant decreases observed in total T4 (21%), free T4 index (16%), T3 (13%), and TBG (23%) (P < 0.02).
- No significant changes in free T4, T3 resin uptake, or TSH levels; patients remained euthyroid, with normal TSH response to TRH in some.
Conclusions:
- Nicotinic acid reduces serum thyroid hormone concentrations while maintaining euthyroid status.
- The observed effect may be partly due to a decrease in thyroxine-binding globulin.
- Further research may be needed to elucidate other potential mechanisms involved.