Thymine Unit Converter

Thymine (also called 5-methyluracil) is one of the four nucleobases that make up DNA. It pairs with adenine and is released into the body when cells break down DNA during normal turnover.

This test measures thymine in urine, normalized to creatinine. Urinary thymine reflects how well the body's pyrimidine degradation pathway is functioning. Under normal conditions, the enzyme dihydropyrimidine dehydrogenase (DPD) efficiently breaks down thymine, keeping urinary levels low.

Elevated urinary thymine most commonly signals a deficiency in DPD, the rate-limiting enzyme in pyrimidine catabolism. This has important implications for cancer treatment, since DPD is also the primary enzyme responsible for metabolizing the chemotherapy drug 5-fluorouracil.

Thymine is released from DNA during normal cell turnover throughout the body. It is then degraded primarily in the liver through the three-step pyrimidine catabolic pathway, with DPD catalyzing the first and rate-limiting step.