A shield-shaped gland and goitre
Goitre, a visible swelling of the neck, appears in ancient Chinese and Greek medical texts, and Chinese sources describe treating it with burnt seaweed. In 1656 the English anatomist Thomas Wharton named the gland "thyroid" after the nearby shield-shaped (Greek thyreos) cartilage. In the 19th century the Swiss surgeon Theodor Kocher made thyroid surgery far safer, and in 1883 he reported lethargy and swelling in patients whose whole thyroid had been removed, helping reveal its function; he received the 1909 Nobel Prize in Physiology or Medicine.
Iodine and thyroid hormones
In 1896 Eugen Baumann discovered that the thyroid is rich in iodine. In 1915 Edward Kendall isolated the hormone thyroxine, and in 1927 Charles Harington and George Barger determined its structure and synthesised it. Thyroid hormones set the metabolic rate of nearly every cell, and thyroid-stimulating hormone (TSH) from the pituitary controls their release. Without enough iodine the gland cannot make hormone and enlarges, and deficiency in pregnancy harms fetal brain development. Between 1917 and 1920 David Marine and Oliver Kimball prevented goitre in Ohio schoolgirls with iodine, and many countries then iodised salt. Diets rich in seaweed, as in Korea and Japan, usually supply ample iodine.
Common disorders and the overdiagnosis debate
In 1912 the Japanese surgeon Hakaru Hashimoto described a disease in which immune cells attack the thyroid; Hashimoto's thyroiditis is a common cause of hypothyroidism, with fatigue, cold intolerance and weight gain. In hyperthyroidism, often from Graves' disease, palpitations, heat intolerance and weight loss occur; in the 1940s Saul Hertz pioneered radioactive iodine treatment. Thyroid nodules found on ultrasound are mostly benign. In South Korea, ultrasound screening in health check-ups in the 2000s made thyroid cancer diagnoses soar while deaths barely changed, and a 2014 paper cited it as a textbook case of overdiagnosis; routine ultrasound screening of people without symptoms is no longer recommended. See an endocrinologist about abnormal thyroid tests or neck lumps.
This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.
FAQ
- Does an underactive thyroid make you gain weight?
- Slower metabolism can add some weight, usually a few kilograms partly from fluid. The thyroid is rarely the main cause of weight gain, so confirm with a test.
- Should I take iodine supplements for my thyroid?
- If your diet includes seaweed or iodised salt, deficiency is uncommon, and too much iodine can itself disturb thyroid function. Ask a doctor before taking supplements.
Sources reviewed: 2026-10-26
References
- Wharton, T. (1656). Adenographia: sive glandularum totius corporis descriptio. London.
- Kocher, T. (1883). Ueber Kropfexstirpation und ihre Folgen. Archiv für klinische Chirurgie, 29, 254–337.
- Baumann, E. (1896). Über das normale Vorkommen von Jod im Thierkörper. Hoppe-Seyler's Zeitschrift für physiologische Chemie, 21, 319–330.
- Hashimoto, H. (1912). Zur Kenntnis der lymphomatösen Veränderung der Schilddrüse (Struma lymphomatosa). Archiv für klinische Chirurgie, 97, 219–248.
- Kendall, E. C. (1915). The isolation in crystalline form of the compound containing iodin, which occurs in the thyroid. JAMA, 64(25), 2042–2043.
- Marine, D., & Kimball, O. P. (1920). Prevention of simple goiter in man. Archives of Internal Medicine, 25(6), 661–672.
- Harington, C. R., & Barger, G. (1927). Chemistry of thyroxine. III. Constitution and synthesis of thyroxine. Biochemical Journal, 21(1), 169–183.
- Hertz, S., & Roberts, A. (1946). Radioactive iodine in the study of thyroid physiology: VII. The use of radioactive iodine therapy in hyperthyroidism. JAMA, 131(2), 81–86.
- Ahn, H. S., Kim, H. J., & Welch, H. G. (2014). Korea's thyroid-cancer "epidemic" — screening and overdiagnosis. New England Journal of Medicine, 371(19), 1765–1767.