Definition of thyroxine in English:



mass nounBiochemistry
  • The main hormone produced by the thyroid gland, acting to increase metabolic rate and so regulating growth and development.

    An iodine-containing amino acid; chemical formula: C₁₅H₁₁NO₄I₄

    • ‘Hormones that require amino acids for starting materials include thyroxine (the hormone produced by the thyroid gland), and auxin (a hormone produced by plants).’
    • ‘When your thyroid gland produces too much of the hormone thyroxine, you develop hyperthyroidism.’
    • ‘He tested for thyrotrophin releasing hormone in 67 women with menorrhagia who had normal concentrations of thyroxine and thyroid stimulating hormone.’
    • ‘Human beings require iodine for the production of the thyroid hormones, thyroxine and triiodothyronine.’
    • ‘The thyroid releases too much of the hormone thyroxine, which increases the person's basal metabolic rate.’


Early 20th century: from thyroid + ox- ‘oxygen’ + in from indole (because of an early misunderstanding of its chemical structure), altered by substitution of -ine.