Nestled in the tissues of your neck is a small unassuming organ that wields enormous power over your body. It's called the thyroid. Like the operations manager in a company, its role is to make sure that the cells in your body are working properly. It does that by using hormones to deliver messages to every single one of them. This high-ranking organ is made up of lobules that each contains smaller cells called follicles, which store the hormones the thyroid sends out into your blood. Two of the most important hormones it produces are thyroxine and triiodothyronine, or T3 and T4. As messengers, the hormone's job is to instruct every cell in the body when to consume oxygen and nutrients. That maintains the body's metabolism, the series of reactions our cells perform to provide us with energy. This hormonal notification from the thyroid gets the heart pumping more efficiently, and makes our cells break down nutrients faster. When you need more energy, the thyroid helps by sending out hormones to increase metabolism. Ultimately, the thyroid allows our cells to use energy, grow and reproduce. The thyroid is controlled by the pituitary gland, a hormonal gland deep in the brain that oversees the thyroid's tasks, making sure it knows when to send out its messengers. The pituitary's role is to sense if hormone levels in the blood are too low or too high, in which case it sends out instructions in the form of the thyroid- stimulating hormone. Even in this tightly controlled system, however, management sometimes slips up. Certain diseases, growths in the thryoid or chemical imbalances in the body can confuse the organ and make it deaf to the pituitary's guiding commands. The first problem this causes is hyperthyroidism, which happens when the organ sends out too many hormones. That means the cells are overloaded with instructions to consume nutrients and oxygen. They become overactive as a result, meaning a person with hyperthyroidism experiences a higher metabolism signaled by a faster heartbeat, constant hunger, and rapid weight loss. They also feel hot, sweaty, anxious, and find it difficult to sleep. The opposite problem is hypothyroidism, which happens when the thyroid sends out too few hormones, meaning the body's cells don't have as many messengers to guide them. In response, cells grow listless and metabolism slows. People with hypothyroidism see symptoms in weight gain, sluggishness, sensitivity to cold, swollen joints and feeling low. Luckily, there are medical treatments that can help trigger the thyroid's activities again, and bring the body back to a steady metabolic rate. For such a little organ, the thyroid wields an awful lot of power. But a healthy thyroid manages our cells so effectively that it can keep us running smoothly without us even noticing it's there.
我々の首にある小さな臓器 体の司令塔ともいえる 甲状腺は 会社にとっての運営部長— 体の細胞が正しく機能するよう 管理する役目をし ホルモンを使って各細胞に指令を送ります この大切な臓器は多くの小葉からなり その中の小胞と呼ばれる小さな細胞は 甲状腺が血管へ送るホルモンを蓄えます 甲状腺が作る2種類の大事なホルモン チロキシン(T4)と トリヨードサイロニン(T3)は メッセンジャーとして 細胞へ酸素と栄養の吸収を指示し 新陳代謝を促し 細胞が一連の反応を通して 体にエネルギーを供給できるようにするのです 甲状腺からのホルモンで 心臓が効率よく血液を循環させるのを助け 細胞が栄養分解をする過程を速やかにします 体がもっとエネルギーを必要とする時は 甲状腺はホルモンを送り 新陳代謝を促進させます 最終的に細胞がエネルギーを使い 成長し再生するのを助けます 甲状腺は 脳深部のホルモン分泌線である 脳下垂体に制御され 必要に応じ体中に指示を出しています 脳下垂体は 血液中のホルモンのレベルが 高すぎないか低すぎないかを感知し 甲状腺刺激ホルモンの形で 体中に指示を送ります これほど綿密な制御体制が敷かれていても 管理が失敗することもあります ある種の病気や 甲状腺内の腫瘍 体内の化学的不均衡が甲状腺を混乱させ 脳下垂体からの指令を無視したりします その1つが甲状腺機能亢進症で 甲状腺からのホルモン過剰分泌が 原因で起きます つまり細胞に 栄養と酸素を摂取する指示が過剰に行き その結果として 新陳代謝が過剰になり 心拍数の増加 過食 体重の急激な減少や また発熱 発汗 不安感 不眠症なども症状として現れます その反対は 甲状腺機能低下症で 甲状腺からのホルモン不足で 細胞に十分な指示が行かず 細胞の働きが鈍り 代謝が低下するのです 症状は体重の増加 倦怠感 冷え性 関節の腫れ うつ などです 幸い 医学療法を使い 甲状腺の働きを正常化させ 体の代謝を健康な状態に戻すことができます 小さな臓器でも 甲状腺はとても支配力があります 正常な甲状腺は細胞を効率的に働かせ 我々がその存在に気付かないほど スムーズに体の健康を保っているのです