Mechanisms or pathogenesis or causes of thyroid disease
| Thyroiditis | Acute thyroiditis | Subacute thyroiditis | Chronic thyroiditis (Hashimoto’s) Silent thyroiditis (painless thyroiditis) Postpartum thyroiditis (probably a variant of silent thyroiditis) NB: Both silent and postpartum thyroiditis are subacute in length (i.e. most patients recover from it) but are not painful like subacute thyroiditis. |
| Hyperstimulation (of the thyroid with TSH receptor antibodies.) | Graves |
| Toxic Nodular Goiter | Toxic Adenoma Toxic Multinodular Goiter |
| Drug-induced: Iodine deficiency, Iodine excess, Lithium, amiodarone, antithyroid drugs. |
May cause goiter, hypothyroidism, or hyperthyroidism. |
| Secondary Hypo/Hyperthyroidism | HYPOTHYROIDISM –Hypothalamic dysfunction (Neoplasms, TB, Sarcoidosis, Hemochromatosis, Radiation treatment, Langerhans cell histiocytosis. –Pituitary dysfunction (Neoplasms, Pituitary surgery, postpartum pituitary necrosis, idiopathic hypopituitarism, glucocorticoid excess (Cushing’s), radiation treatment to the pituitary.HYPERTHYROIDISM -TSH-secreting pituitary tumor; |
| Congenital | Thyroid agenesis; Thyroid dysgenesis; Hypoplastic thyroid, Biosynthetic defects, etc. |
| Solitary thyroid nodule (Neoplasm) | Noncancerous thyroid neoplasm that is not a toxic nodule. |
| Thyroid Cancer | Papillary Thyroid Cancer (80%) – the most common type of thyroid cancer, accounting for about 80% of cases. They are slow growing. Develop from follicular cells. Follicular Thyroid Cancer (10%). The 2nd most common type of thyroid cancer, and accounts for about 10% of cases. “In most cases, it is associated with a good prognosis, although it is somewhat more aggressive than papillary cancer. Follicular carcinomas do not usually spread to nearby lymph nodes, but they are more likely than papillary cancers to spread to other organs, like the lungs or the bones.” Hurthle Cell Thyroid Cancer (3%). Is a subtype of follicular carcinoma. It makes up about 3% of thyroid cancer. Medullary Thyroid Cancer (4%). Develops from C cells in the thyroid gland. Is less differentiated and more aggressive than papillary or follicular cancers. About 4% of all thyroid cancers. They also frequently release high levels calcitonin and carcinoembryonic antigen (CEA) which can be seen in lab tests. Anaplastic Thyroid Cancer (2%). It is the most undifferentiated type of thyroid cancer (meaning that it looks the least like normal cells of the thyroid gland). It is thus the most aggressive and quickly spreads to other parts of the neck and body. |
| An ectopic site produces thyroid hormones or analogs. | Struma ovarii – ovarian teratoma that has tissue that secretes thyroid hormone. Hydatidiform mole – Human chorionic gonadotropin (beta- hCG) the mole produces has intrinsic TSH-like activity. |
| Exogenous | HYPERTHYROIDISM Iatrogenic (Patient is given too much by their provider to treatment legitimate condition); Factitious Thyrotoxicosis; Intentional or accidental overdose HYPOTHYROIDISM: Iodine therapy Thyroidectomy |
Thyroiditis – See this link for four types of thyroiditis.
Clinical Presentation of Thyroid Disease
- Hypothyroidism – Hashimotos’ thyroiditis is the most common cause of hypothyroidism.
- Subclinical Hypothyroidism
- Hyperthyroidism – Graves is the most common cause of hyperthyroidism in the U.S. Followed by Toxic nodular goiter.
- Subclinical Hyperthyroidism.
- Thyroid cancer.
Goiters – Can be seen with hypothyroidism (most commonly) or hyperthyroidism. Goiter simply means an enlargement of your thyroid gland.
Thyroid Gland Facts
-The normal thyroid gland produces about 80% T4 and about 20% T3, however, T3 possesses about four times the hormone “strength” or “activity” as T4. In the tissues, T4 is converted (de-iodinated) to T3.
– More than 99% of T4 & T3 are bound in serum, mostly to TBG.
-Free T4 best reflects the amount of hormone available to the tissues.
-Most thyroid disorders are 2/2 to thyroid gland d/o (i.e. they are primary), rather than from central (secondary) causes.
-Thyroid peroxidase (TPO) is an enzyme found in the thyroid follicle cells where it converts the thyroid hormone T4 to T3.
Resources:
http://www.medicinenet.com/thyroid_pictures_slideshow/article.htm
http://www.aafp.org/afp/2016/0301/p363.html
http://www.thyroid.ca/thyroid_gland.php
https://www.endocrineweb.com/conditions/thyroid/all
http://www.thyroid.ca/thyroiditis.php
http://emedicine.medscape.com/article/125648-overview
http://www.cancercenter.com/thyroid-cancer/types/