Thyroiditis

# Overview
Thyroiditis refers to an inflammation of the thyroid gland. It is classified into Hashimoto's thyroiditis, de Quervain's Thyroiditis, silent thyroiditis, postpartum thyroiditis, Riedel's thyroiditis, and suppurative thyroiditis. These forms of thyroiditis can be differentiated from each other on the basis of pathological and laboratory findings. Thyroiditis can lead to hypothyroidism or transient hyperthyroidism. The hypothyroid phase of thyroiditis results from the gradual depletion of stored thyroid hormones. Chronic hypothyroidism is predominantly associated with hashimotos thyroiditis. However, all the types of thyroiditis may progress to permanent hypothyroidism. Painless sporadic thyroiditis (silent thyroiditis), painless postpartum thyroiditis, and painful subacute thyroiditis (de Quervain's thyroiditis) usually lead to transient hyperthyroidism (thyrotoxicosis) when the preformed thyroid hormones are released from the damaged gland. As thyroid hormone stores are depleted, there is often a progression through a period of euthyroidism to hypothyroidism. Suppurative thyroiditis is the result of an infection usually in the patients with preexisting thyroid disease (Hashimoto's thyroiditis, thyroid cancer, or multinodular goiter), immunosuppression, and congenital anomalies (pyriform sinus fistula). The diagnosis of thyroiditis is usually made on the physical examination, thyroid function tests, thyroid ultrasound, iodine uptake, thyroglobulin, and thyroid peroxidase antibodies. Histopathological analysis is also helpful to differentiate thyroiditis from other thyroid diseases. The treatment of thyroiditis is usually symptomatic. Beta blockers are used for the symptoms of thyrotoxicosis and levothyroxine is helpful to improve the symptoms of hypothyroidism. NSAIDs are helpful in alleviating the pain in de Quervain's thyroiditis and corticosteroids are specifically used in Riedel's thyroiditis. Antibiotics are usually reserved for the suppurative thyroiditis.

# Classification
Thyroiditis is classified into the following types:
- Hashimoto's thyroiditis
- De Quervain's Thyroiditis or granulomatous thyroiditis
- Silent thyroiditis
- Postpartum thyroiditis
- Riedel's thyroiditis
- Suppurative thyroiditis

# Differentiating Thyroiditis from Other Diseases
Various forms of thyroiditis can be differentiated from each other on the basis of pathological and laboratory findings:

## Differentiating thyroiditis from other causes of hypothyroidism
- The diagnosis of thyroiditis is usually made on the physical examination, thyroid function tests and various other diagnostic tests are listed in the table below:
:T3RU; Triiodothyronine Resin Uptake
^: TPOAb; Thyroid peroxidase antibodies
*: TSH may be decreased transiently in the thyrotoxicosis
: TPOAb may be present in drug-induced hypo/hyperthyroidism such as Interferon-alpha, interleukin-2, and lithium

## Differentiating thyroiditis causing thyrotoxicosis from other causes of hyperthyroidism
- Hashimoto's thyroiditis can initially present with thyrotoxicosis (hashitoxicosis) which must be differentiated from other causes of thyrotoxicosis.
T3RU; Triiodothyronine Resin uptake
^TPOAb; Thyroid peroxidase antibodies

# Diagnosis
The following flowchart describes the clinical approach to the diagnosis of thyroiditis.

## Stepwise clinical diagnosis of thyroiditis
TFT: Thyroid function tests (TSH, T4, and T3)
: Grave's disease is not a thyroiditis
*: RAIU; Radioiodine uptake
: One third of Riedel's thyroiditis presents with hypothyroidism

# Treatment

## Treatment of Hashimoto's thyroiditis
The drugs used in the treatment of Hashimoto's thyroiditis are:
Levothyroxine:
- lifelong synthetic levothyroxine (L-T4) is used to treat the hypothyroidism in Hashimoto's disease.
- Main goals of levothyroxine replacement therapy are:
Resolution of the hypothyroid symptoms and signs including biological and physiologic markers of hypothyroidism
Normalization of serum thyrotropin with improvement in thyroid hormone concentrations
To avoid overtreatment (iatrogenic thyrotoxicosis)
- Resolution of the hypothyroid symptoms and signs including biological and physiologic markers of hypothyroidism
- Normalization of serum thyrotropin with improvement in thyroid hormone concentrations
- To avoid overtreatment (iatrogenic thyrotoxicosis)
- Side effects include atrial fibrillation and osteoporosis
Corticosteroids:
- A short course of glucocorticoids can be used in the treatment of IgG4-related variant of Hashimoto's thyroiditis.
Selenium:
- Dietary selenium supplementation is considered to be protective against the autoimmune diseases of the thyroid.

### Drug Regimen for Hashimoto's thyroiditis
- Synthetic levothyroxine (L-T4) 1.61.8 g/kg of body weight per day orally.

## Treatment of de Quervain's thyroiditis thyroiditis
The drugs used in the treatment of de Quervain's thyroiditis are:
- NSAIDs
- Prednisone
- Atenolol
- Synthetic levothyroxine

### Drug Regimens for de Quervain's thyroiditis
- For pain
Preferred regimen (1): Naproxen: 500 to 1000 mg per day in two divided doses
Preferred regimen (2): Ibuprofen: 1200 to 3200 mg per day in three or four divided doses
- Preferred regimen (1): Naproxen: 500 to 1000 mg per day in two divided doses
- Preferred regimen (2): Ibuprofen: 1200 to 3200 mg per day in three or four divided doses
- For severe condition
Preferred regimen (1): Prednisone: 40 mg per day orally
- Preferred regimen (1): Prednisone: 40 mg per day orally
- For hypothyroidism
- Preferred regimen (1): Synthetic levothyroxine (L-T4): 1.61.8 g/kg per day orally
- For thyrotoxic symptoms
Preferred regimen (1): atenolol: 25-200mg per day orally
Preferred regimen (2): metoprolol: 25-200mg per day orally
- Preferred regimen (1): atenolol: 25-200mg per day orally
- Preferred regimen (2): metoprolol: 25-200mg per day orally

## Treatment of silent thyroiditis
The drugs used in the treatment of silent thyroiditis are:
- Atenolol
- Metoprolol
- Synthetic levothyroxine

### Drug Regimen for silent thyroidits
- For thyrotoxic symptoms
Preferred regimen (1): atenolol: 25-200mg per day orally
Preferred regimen (2): metoprolol: 25-200mg per day orally
- Preferred regimen (1): atenolol: 25-200mg per day orally
- Preferred regimen (2): metoprolol: 25-200mg per day orally
- For hypothyroidism
- Preferred regimen (1): Synthetic levothyroxine (L-T4): 1.61.8 g/kg per day orally

## Treatment of Riedel's thyroidtis
- The drugs used in the treatment of silent thyroiditis are:
- Corticosteroids
- Tamoxifen
- Mycophenolate mofetil(used in combination with corticosteroids)

### Drug Regimens for Riedel's thyroidtis
The effectiveness of therapy and dosages for Riedel's thyroiditis have not yet been assessed completely. As a result, the exact dosage regimens and duration of therapy cannot be defined. The current recommendations are based on the clinical manifestations, associated conditions, and the response to treatment.
- Preferred regimen (1): Prednisone 15-60mg PO q24h for 6 months to 2 years
- Preferred regimen (2): Prednisone 500 mg PO q24h for 6 months to 2 years
- Alternative regimen (1): Tamoxifen 10-20 mg PO q24h for 6 months to 2 years
- Alternative regimen (1): Mycophenolate mofetil 1 g PO q12h for 6 months to 2 years

# Related Chapters
- Hypothyroidism
- Hyperthyroidism
- Graves-Basedow disease