Subacute thyroiditis

Japanese: 亜急性甲状腺炎 - あきゅうせいこうじょうせんえん（英語表記）Subacute thyroiditis

What is the disease?

This is a disease in which the thyroid gland becomes inflamed. The overall course of the disease is between acute and chronic, lasting about 2 to 4 months, so it is called subacute thyroiditis.

What is the cause?

It is thought to be a viral infection, but this has not been proven.

How symptoms manifest

I feel pain in the thyroid area (front of the neck). The prodromal symptoms are similar to those of a cold, and the onset of the condition occurs suddenly after 2-3 weeks.

The characteristic feature is neck pain, and spontaneous pain and tenderness in the thyroid gland. Auricle ( Next ) Since the pain extends to the back and occipital region of the head, patients often visit a neurologist, orthopedic surgeon, otolaryngologist, or dentist.

The pain can range from a slight pain when yawning or stretching the neck to a pain so severe that even touching the neck makes you jump. The thyroid gland is hard and swollen, and it hurts when pressed. The painful area may also move from side to side. The fever can range from a slight fever to a high fever of nearly 40°C.

If the thyroid gland is severely damaged, thyroid hormones will leak into the bloodstream. Hyperthyroidism ( Factory inspection report ) Symptoms of rhinitis, especially severe generalized Fatigue ( Health test ) Symptoms such as palpitations and trembling hands may be observed, making you feel as if you have a serious illness. However, the hormones stored in the thyroid gland are only enough for about one month, so the symptoms of hyperthyroidism will eventually subside naturally. After hyperthyroidism, your thyroid may become hypoactive for a period of time before returning to normal.

Testing and diagnosis

The diagnosis is easy if you notice pain in the thyroid gland, as it has specific symptoms. Adenoma ( player ) There is bleeding in the area, and a blood blister-like cyst ( Cyst ( News ) ) may cause similar pain. If an ultrasound scan shows a hypoechoic area at the site of pain, it can be diagnosed as subacute thyroiditis. Blood tests will also show positive inflammatory responses such as erythrocyte sedimentation rate and CRP.

When hormones stored in the thyroid gland leak into the blood, thyroid hormones become high and thyroid-stimulating hormone (TSH) becomes low. This result is the same as Graves' disease, but TSH rarely falls below the measurement limit and TSH receptor antibody (TRAb), the causative substance of Graves' disease, is negative, so it can be distinguished from Graves' disease.

Treatment methods

Since this is a disease that heals naturally, symptomatic treatment is the main focus. Salicylic acid preparations are administered for fever and pain. If the pain is severe, corticosteroids may be administered. In this case, the pain and fever will disappear within 1-2 days, but if the medication is reduced or stopped too soon, the symptoms will recur, so the medication will be taken for a relatively long period of time.

For palpitations, β ( beta ) Blocking drugs may also be used.

What to do if you notice an illness

It is a disease with characteristic symptoms that are relatively easy to identify, but it is often misdiagnosed. If you have pain in your thyroid gland, it is a good idea to ask your doctor if it could be subacute thyroiditis.

Yoshifumi Abe

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　甲状腺に炎症が起こる病気で、全経過が2～4カ月くらいで急性と慢性の中間なので、亜急性甲状腺炎と呼ばれています。

原因は何か

　ウイルスの感染と考えられていますが、証明はされていません。

症状の現れ方

　甲状腺の部位（首の前）に痛みを感じます。前駆症状として、かぜのような症状があり、2～3週間してから急に発症します。

　特徴的なのは首の痛みで、甲状腺に自発痛や圧痛が認められますが、患者さんは耳介(じかい)後部や後頭部まで痛くなるので、神経内科、整形外科、耳鼻科、歯科などを受診することもよくあります。

　痛みは、あくびをしたり首を伸ばしたりするとちょっと痛いといった程度のものから、少し首に触っただけで飛び上がるほど痛いといったものまでがあります。甲状腺は硬くはれて、押すと痛みがあります。また、痛い場所が左右に移動することがあります。熱は、微熱から40℃近い高熱が出ることまであります。

　甲状腺の破壊の程度が激しいと甲状腺ホルモンが血液中に流れ出すので、甲状腺機能亢進症(こうじょうせんきのうこうしんしょう)の症状、とくに強い全身の倦怠感(けんたいかん)、動悸、手の震えなどが認められ、重い病気になったという感じがします。しかし、甲状腺にたまっているホルモンはせいぜい1カ月分くらいなので、甲状腺機能亢進症の症状はやがて自然におさまります。甲状腺機能亢進症のあと一時期、機能低下症になってから正常になることもあります。

検査と診断

　特有な症状があるので、甲状腺に痛みがあることに気がつけば診断は容易です。しかし、甲状腺内にある小さな腺腫(せんしゅ)のなかに出血して血豆のようなシスト（嚢胞(のうほう)）ができると似たような痛みを起こすことがあります。超音波断層検査で痛みの部位に低エコー部が確認できれば、亜急性甲状腺炎と診断できます。また血液検査では赤沈、CRPなどの炎症反応が陽性になります。

　甲状腺の中に蓄積されているホルモンが血中にもれると甲状腺ホルモンが高値になり、甲状腺刺激ホルモン（TSH）が低値となることがあります。この結果はバセドウ病と同じですが、TSHが測定限界以下にまで下がることは少なく、バセドウ病の原因物質であるTSHレセプター抗体（TRAb）が陰性なので、バセドウ病と区別できます。