【Thyroid cancer】
 it is most common after age 30.

Common types of the benign thyroid nodules are adenomas (overgrowths of normal thyroid tissue), thyroid cysts, thyroiditis, and autoimmune disorder.Papillary carcinoma accounts for 60%, follicular carcinoma accounts for 12%, and the follicular variant of papillary carcinoma accounts for 6%. 

well differentiated thyroid cancers are usually curable.

Fine needle biopsy(FNAB) is a safe, effective, and easy way to determine if a nodule is cancerous. FNAB is the most important diagnostic tool in evaluating thyroid nodules and should be the first intervention. The following are the 4 possible results from this procedure:

● Benign disease
● Malignant disease
● Indeterminate for diagnosis
● Nondiagnostic

Up to 50% of repeated biopsies result in a definitive diagnosis. Patients whose findings are indeterminate or nondiagnostic despite repeat biopsy can undergo surgery for lobectomy for tissue diagnosis.

Nondiagnostic cases can also be monitored clinically, and radioiodine scans can be useful for determining the functional status of the nodule, because most hyperfunctioning nodules are benign. An estimated 5-10% of solitary thyroid nodules are malignant. Palpable and nonpalpable nodules of similar size have the same risk of malignancy.

The Following Features Favor a Benign Thyroid Nodule:
> Family history of Hashimoto's thyroiditis
> Family history of benign thyroid nodule or goiter
> Symptoms of hyperthyroidism or hypothyroidism
> Pain or tenderness associated with a nodule
> A soft, smooth, mobile nodule
> Multi-nodular goiter without a predominant nodule (lots of nodules,    not one main nodule)
> "Warm" nodule on thyroid scan (produces normal amount of hormone)
> Simple cyst on an ultrasound

The Following Features Increase the Suspicion of a Malignant Nodule:
> Age less than 20
> Age greater than 70
> Male gender
> New onset of swallowing difficulties
> New onset of hoarseness
> History of external neck irradiation during childhood
> Hard and fixed nodules are more suggestive of malignancy 
> Presence of cervical lymphadenopathy (swollen, hard lymph nodes in  the neck)
> Previous history of thyroid cancer
> Nodule that is "cold" on scan (shown in picture above, meaning the nodule does not make hormone)
> Solid or complex on an ultrasound

radioactive iodine uptake x ray (thyroid scan)
If a nodule is composed of cells that do not make thyroid hormone (don't absorb iodine), then it will appear "cold" on the x-ray film. A nodule that is producing too much hormone will show up darker and is called "hot."

85% of thyroid nodules are cold, 10% are warm, and 5% are hot.  85% of cold nodules are benign, 90% of warm nodules are benign, and 95% of hot nodules are benign. So, the presence of hyperthyroidism favors a benign nodule , but, malignant disease cannot be ruled out .

Thyroglobulin levels are useful tumor markers once the diagnosis of malignancy has been made, but they are non-specific in regard to differentiating a benign from a cancerous thyroid nodule. Ultrasound alone cannot differentiate benign from malignant nodules.  since 15% of cystic thyroid nodules are malignant.Thyroid fine needle aspiration (FNA) biopsy is the only non-surgical method that can differentiate malignant and benign nodules .

【Thyroiditis】
thyroiditis includes
(1) acute suppurative thyroiditis, which is due to bacterial infection;
(2) subacute thyroiditis, which results from a viral infection of the gland, or autoimmune.
(3) chronic thyroiditis, which is usually autoimmune in nature.

In childhood, chronic thyroiditis is the most common 
 
【Subacute thyroiditis】
Subacute thyroiditis are recognized to 3 types:
1. Subacute granulomatous thyroiditis - Also known as subacute painful
2. Subacute lymphocytic thyroiditis - Also known as subacute painless thyroiditis
3. Subacute postpartum thyroiditis

The thyroid function of subacute thyroiditis contains these stages:
Thyrotoxicosis persist about 1-2 months ,After the thyroid is depleted of thyroid hormone, patients' serum levels of T4 and T3 decrease into the hypothyroid range.  is usually mild but persists for 2 months. Supplementation with thyroid hormone is necessary only if the patients become symptomatic from the hypothyroidism. Ninety to 95% of patients spontaneously return to normal thyroid function.

A ratio of T3 to T4 of less than 15 usually increases suspicion of subacute thyroiditis. Otherwisw graves disease RAIU is decreased in subacute thyroditis,  but  increased in graves disease. Antithyroid drugs is not indicated in patients with subacute thyroiditis  beta blockers may be indicated for the symptomatic treatment of thyrotoxicosis. 

Replacement of thyroid hormone in the hypothyroid phase is indicated if the patient's symptoms are severe or of long duration.7 
If the hypothyroid phase lasts longer than six months, permanent hypothyroidism is likely.11 

【Subacute granulomatous thyroiditis】
The most accepted etiology for this condition is a viral illness. Subacute granulomatous thyroiditis is the most common cause of a painful thyroid gland.  The thyroid is firm, nodular and exquisitely tender to palpation. 

The transient presence of autoantibodies (eg, Thyroid peroxidase antibodies (TPO Ab) and  Antithyroglobulin antibody(Tg Ab) )have been noted in the acute phase of the disease, but this has been attributed to a virally induced immune response.

The hallmarks of subacute granulomatous thyroiditis are a very high ESR, often as high as 60-100, thyroid is painful. A normal ESR essentially rules out the diagnosis of subacute granulomatous thyroiditis. The physical examination, an elevated ESR, an elevated thyroglobulin level and a depressed RAIU confirm the diagnosis.(目前我們診所只能用T3/T4 <20, ESR, tenderness 等3種表現來確定診斷)

Nonsteroidal anti-inflammatory drugs are generally effective. A tapering dosage of  prednisone (20 to 40 mg per day) given over two to four weeks.for severe painful case.

【Subacute lymphocytic thyroiditis】
(also referred to as Hashimoto's thyroiditis)
 
This condition is likely autoimmune in nature, A painless goiter. Thyroid peroxidase antibodies (TPO Ab) and Antithyroglobulin antibody(Tg Ab) )have been noted higher than Subacute granulomatous thyroiditis the ESR is within the reference range and the thyroid is not painful most likely is autoimmune in nature. Patients develop an permanent hypothyroidism more often than they do with subacute granulomatous thyroiditis.

An HLA association may be present, suggesting a genetic predisposition , or Certain drug exposures   include amiodarone , and lithium. Subacute lymphocytic thyroiditis with hyperthyroidism can be diagnosed by taking a radioactive iodine uptake test (RAIU) test. Which differentiate  from  Graves' disease. (目前我們診所只能用T3/T4 <20,來確定診斷)

Subacute postpartum thyroiditis with hyperthyroidism can be diagnosed by taking a radioactive iodine uptake test (RAIU) test. Which differentiate  from  Graves' disease. (目前我們診所只能用T3/T4 <20,來確定診斷)

【Subacute postpartum thyroiditis】
This condition is likely autoimmune in nature. 

women with postpartum thyroiditis:
An isolated hypothyroid phase occurs in 48% isolated thyrotoxicosis is found in 30% patients, hyperthyroidism followed by hypothyroidism is seen in 22% of them. Patients develop an permanent hypothyroidism more often than they do with subacute granulomatous thyroiditis. The ESR is within the reference range and the thyroid is not painful, which distinguishes this condition from subacute granulomatous thyroiditis. 

【Graves Disease】
Graves disease, is an autoimmune disease.

Graves disease, Hashimoto thyroiditis, and sbacute lymphocytic thyroditis are autoimmune thyroid disorder.  All have a family history.

4 well-known thyroid antigens: thyroglobulin, thyroid peroxidase, sodium-iodide symporter and the thyrotropin receptor. However, the thyrotropin receptor itself is the primary autoantigen of Graves disease and is responsible for the manifestation of hyperthyroidism.

Maternal Graves disease can lead to neonatal hyperthyroidism by transplacental transfer of thyroid-stimulating antibodies. Elderly individuals may develop apathetic hyperthyroidism, and the only presenting features may be unexplained weight loss or cardiac symptoms such as atrial fibrillation and congestive heart failure. Typically, Graves disease is a disease of young women, but it may occur in persons of any age.

by ultrasonography:
Graves disease shows a hypoechoic thyroid, with diffuse, increased vascular flow shown by Doppler ultrasonography. Subacute thyroiditis during the acute phase shows a hypoechoic thyroid, with heterogeneity, decreased vascular flow shown by Doppler ultrasonography. The natural history of Graves disease is that most patients become hypothyroid and require replacement. 

【Hashimoto's Thyroiditis】
The first sign of the disease is often an enlarged thyroid, called a goiter.  The thyroid gland is typically goitrous but may be atrophic or normal in size. 

Antibodies binding to and blocking the thyroid-stimulating hormone (TSH) receptor, thyrotropin receptor blocking antibodies (TBII) have also been described and may contribute to impairment in thyroid function.

Up to 15% of patients aged 65 years or older may have subclinical hypothyroidism (mild thyroid failure, as evidenced by an elevated TSH above 4.0 μ IU/mL and normal free T4 levels) The best marker of progression to overt hypothyroidism is a combination of an elevated TSH level with the presence of thyroid autoantibodies, namely anti-TPO and anti-Tg antibodies. Perform fine-needle aspiration of any dominant or suspicious thyroid nodules to exclude malignancy or the presence of a thyroid lymphoma in fast-growing goiters.