TOKYO -- Singer and actor Ayumi Ishida, best known for hits such as "Blue Light Yokohama," died at a hospital in Tokyo in March at age 76 due to hypothyroidism, a type of thyroid hormone deficiency. Her death prompted specialists to highlight the importance of early detection of this disease, which is relatively common among women, yet seldom fatal.

The thyroid gland, weighing about 20 grams and located under the Adam's apple, resembles the shape of a butterfly with wings spread open. It secretes thyroid hormones, which control the body's energy metabolism. Thyroid hormones circulate through the bloodstream to all parts of the body, promoting metabolism and growth functions essential to human health.

According to Noritaka Onoda, head of Shinjuku Kanazawa Naika Clinic in Tokyo's Shinjuku Ward and a thyroid specialist certified by the Japan Thyroid Association, the amount of thyroid hormones secreted is regulated by thyroid-stimulating hormone (TSH) from the pituitary gland. Normally, secretion remains constant, but if an abnormality occurs, it shifts to excessive or insufficient levels. Such anomalies are typically detected by blood tests measuring concentrations of TSH and two thyroid hormones (known as FT3 and FT4).

Diseases involving an excess of thyroid hormone production are referred to as hyperthyroidism. One notable example, Graves' disease, is characterized by symptoms including palpitations and feeling uncomfortably hot. Conversely, insufficient thyroid hormone production leads to hypothyroidism.

10% of women have autoantibodies

A common example of hypothyroidism is Hashimoto's disease, or chronic thyroiditis, a condition in which antibodies of one's own immune system mistakenly attack the thyroid gland. Approximately one in every 10 adult women has such antibodies, known as autoantibodies. Chronic inflammation prevents the thyroid from producing adequate hormone levels.

Symptoms widely vary: apathy, fatigue, swelling, chills, weight gain, sluggish movements, reduced memory function, hair loss, dry skin and brittle nails are common manifestations, though their severity differs individually.

However, early-stage hypothyroidism symptoms are easily mistaken for simple tiredness or mental unease, making self-detection challenging. "Thyroid hormone levels can be easily checked with a blood test. Those experiencing relevant symptoms should undergo examination," Onoda advised.

Neglecting or halting treatment a taboo

Death from hypothyroidism is apparently rare. "Typically, symptoms subside once patients begin medication to replenish the deficient thyroid hormone, enabling them to lead normal lives. If there is no problem with values in regular checkups and their physical condition is fine, there is generally no cause for concern," Onoda noted.

So when is hypothyroidism dangerous? Speaking in general terms and noting Ayumi Ishida's circumstances might not correspond directly, Onoda explained, "If severe thyroid hormone deficiency goes untreated over prolonged periods or if treatment is interrupted, a dangerous condition called myxedema coma can arise." Characterized by loss of consciousness with low body temperature and respiratory depression or inadequate breathing, its mortality rate is a steep 30%. Complications associated with other serious underlying illnesses, infectious diseases or injuries often act as triggers.

Meanwhile, there are essential precautions for patients diagnosed with hypothyroidism. The disease tends to progress slowly. If the patient's symptoms suddenly worsen, it might indicate another underlying cause. Elderly people, who more frequently struggle with multiple illnesses, should be particularly cautious. "If you are diagnosed with hypothyroidism, it is crucial not to stop taking medication based on your own judgment and to consult your primary care physician if you have any concerning symptoms," Onoda said.

(Japanese original by Reiko Ide, Lifestyle, Science & Environment News Department)