Thyroid diseases Flashcards
Which endocrine gland is superficial?
The thyroid gland
What are the functions of the thyroid hormone?
1) Increases glucose in the blood and its uptake
2) Increases fatty acids in the blood due to its induction of lipolysis and increases its uptake by the liver
3) Normally it causes protein anabolism but in HYPERthyroidism it would cause protein destruction, whether muscle or the heart
4) Increases the basal metabolic rate
5) Increases O2 consumption by all body tissues
6) It is needed for all kinds of development whether physical, mental, or sexual
7) It increases the potency of catecholamines such as epi & Norepi which is why one of the treatments we give to HYPERthyroidism patients are beta-blockers
8) Increases HR, the force of contractions, and everything in the CVS but again in HYPERthyroidism due to its protein catabolism effect it would destroy the heart therefore decreasing everything
9) Increases alertness in the CNS but in hyperactive cases, it can cause nervousness and even tremors
10) Increases GIT motility so in hyperactive cases can cause diarrhea
What is meant by thyrotoxicosis?
An increase in thyroid hormone due to anything
What is the cause of hyperthyroidism?
When there is thyrotoxicosis with hyperthyroidism
- It could be primary or secondary
What are the different primary causes of hyperthyroidism?
1) Graves’ disease
2) Toxic multinodular goiter
3) Toxic adenoma of the thyroid
What are the secondary causes of hyperthyroidism?
Pituitary adenoma secreting TSH
What is thyroiditis?
Destruction of the follicular cells due to an inflammatory process leading to transient thyrotoxicosis due to the release of T3 & T4 independent of a hyperactive gland
- Thyroiditis in the beginning causes hyperthyroidism but after continuous destruction, you’ll have no more glands left hence you end up with hypothyroidism
What is meant by a toxic multinodular goiter?
The nodules in the thyroid gland are enlarged and if it starts releasing thyroid hormone it becomes “Toxic”
What are the manifestations of hyperthyroidism?
1) Calorinergic effects:
- Heat intolerance
- Soft, warm, flushed skin
- Weight loss despite increased appetite
2) Systemic:
- CVS: inc.HR, Cardiomyopathy, valvulopathy
- NMS: Nervousness, Tremors, Irritability, Muscle weakness
- GIT: Diarrhea + Steatorrhea (Fat in still, described as not easily flushed with a foul smell)
- Thyroid: Goiter (not seen in thyroiditis)
3) Raises serum calcium (like in nephrogenic DI where we have hypercalcemia and hypokalemia)
4) Raised blood glucose serum (it also increases it uptake and increases the insulin metabolism)
5) Lowers the cholesterol (increases the uptake by the liver, which could lead to gallstones)
6) Contraction of the eyelid muscle making a wide stare gaze
What are the investigations of hyperthyroidism?
1) Serum TSH
- First line, if it is low then primary or thyroiditis “due to negative inhibition”, if it is high then secondary
2) Free T3 & T4 hormone assay
3) Measuring the activity by seeing the uptake of radioactive Iodine (diffuse uptake in Graves disease, only the adenoma in toxic adenoma, in Toxic MNG only the nodules will uptake it, low uptake thyroiditis)
What is Graves disease?
- Most common cause of hyperthyroidism
- Autoantibodies against TSH receptor stimulating the thyroid gland
- There is a triad in Graves disease
1) Hyperthyroidism “diffuse hyperplasia
2) Infiltrative ophthalmology (leads to exophthalmos)
3) Localized dermopathy (pretibial myxedema “Scaly thickening of the dermis due to deposition of GAGs and infiltration by lymphocytes”)
What is the pathogenesis of graves disease?
1) Autoantibodies against the TSH receptor (TSI), will lead to hyperthyroidism in three different ways:
1a) TSI binds to TSH receptor increasing the secretion of thyroid hormones
1b) Thyroid growth-stimulating Ig, binds to TSH receptor proliferation of thyroid follicular epithelium = diffused hyperplasia
1c) TSH-binding inhibitor Ig:
- This could stimulate the thyroid function (hyperthyroidism) and it can also inhibit it leading to (hypothyroidism)
What are the different types of immunoglobulins found in graves disease?
1) Thyroid-stimulating IgG
- Binds to TSH receptors to release the hormone
2) Thyroid growth-stimulating Ig
- Causes hyperplasia of the gland
3) TSH-binding inhibitor Ig
- Firstly, it blocks the TSH receptors and prevents the normal TSH from binding, then sometimes it will mimic the TSH and trigger the release of thyroid hormone and sometimes it BLOCKS its action even from its autoantibody brothers. This is why patients with graves have attacks of Hyper AND hypothyroidism
Exopthalmous is due to infiltrative ophthalmology, what is infiltrative ophthalmology?
- When the volume of the retroorbital connective tissue and the extraocular muscles increase in volume and mass due to:
1) Infiltration via T-cells
2) Accumulation of hydrophilic glycosaminoglycans
3) Increase in adipocytes
What are the changes in the thyroid gland that occur?
1) Grossly:
- Diffuse and systemic enlargement of the thyroid
2) Microscopically:
- Thyroid follicles follicular epithelial cells that are crowded with small papillae that do not have a fibrovascular core (pseudo papillae)
- Colloid with scalloped margin
- Stroma is infiltrated by lymphocytes, plasma cells with the formation of lymphoid follicles
Summarize graves disease
- Triad (hyperthyroidism, exophthalmos, pretibial myxedema)
- Gross diffuse hyperplasia, microscopic pseudo papillae with colloid scalloped border
What are the different causes of hypothyroidism?
1) Primary
1a) Congenital (like in thyroid dysgenesis or Dyshormonogenetic goiter)
1b) Autoimmune (Hashimoto thyroiditis)
1c) Iatrogenic (Surgical or in radiation-induced ablation of the thyroid parenchyma)
2) Secondary
- Arises from a hypothalamic or pituitary disease
What are the clinical manifestations of hypothyroidism?
1) Cretinism (hypothyroidism in infancy or early childhood)
2) Dwarf
3) Puffiness of the eyelids
4) Depressed nasal bridge
5) Big lips
6) Protruding tongue
7) severe mental retardation
8) Impotent
9) Myxedema (hypothyroidism in older children and adults)
10) Calonergic effects (like cold intolerance, decreased sweating, dry cold skin, loss of outer 1/3 of the eyebrows, brittle nails, weight gain)
11) Systemic: (Decreased HR, CO, slow mentation, poor memory, hypersomnia, steatorrhea, galactorrhea, goiter, Hypoglycemia, hyperprolactinemia “Galactorrhea? This means increased prolactin but what is the link? Low T3 & T4 will stimulate positive feedback to release TRH and when this is elevated it will induce more TSH + GH + PL. So expect to see galactorrhea and gynecomastia”)
Describe the pathogenesis of Hashimoto thyroiditis
- The mechanisms of thyrocyte death are:
1) T-cell mediated cell death (CD8+ cytotoxic T-cells, Type 4 hypersensitivity rxn)
2) Cytokine-mediated cell death (Increased number of CD4+, recruiting and activating macrophages)
3) Antibody-dependent cell-mediated cytotoxicity (anti-thyroglobulin and antithyroid peroxidase antibodies “Type-2 hypersensitivity)
What are the clinical presentations of Hashimoto thyroiditis?
1) Hypothyroidism (decreased T3 & T4, while there is an increased in TSH)
2) Hashtoxicosis (sometimes preceded by hyperthyroidism, it has an increased T3, and T4 while a decreased TSH)
Describe the morphology of Hashimoto thyroiditis
1) Gross:
- Diffuse and symmetric enlargement of the thyroid
2) Microscopically:
- The thyroid follicles are atrophied and lined with hurthle cells “follicular cells that tried to fight off the lymphocytes by becoming big cells with red cytoplasm”(eosinophilic cytoplasm)
- Scanty colloid
- The stroma is filled with inflammatory cells (lymphocytes, plasma cells) + formation of lymphoid follicles
- Fibrosis
Summarize Hashimoto thyroiditis
- Hyperthyroidism then hypo
- Grossly diffuse enlargement and microscopically lymphocytes + Hurthle cells (Hurthle cells are the follicular cells that tried to fight off the lymphocytes by becoming big cells with red cytoplasm)
How to differentiate between Graves disease and Hashimoto?
Hashimoto can have T-cell infiltration but in graves, there are no T-cells
Summarize the causes of Hashimoto’s thyroiditis
1) CD8+ cytotoxic cell-mediated cytotoxicity
2) Cytokine-mediated thyrocyte injury
3) Antibody-dependent cell-mediated cytotoxicity
What are the different causes of goiter?
1) Endemic:
- Colloid goiter
- iodine deficiency (in geographic areas where the iodine is low, the thyroid gland can’t make the thyroid hormone so to compensate TSH will increase enlarging the gland)
- Goitrogens (ingestion of substances that interfere with the synthesis of the thyroid hormone)
2) Sporadic, females
- Physiologically like in adolescence, pregnancy (where there is an increased metabolic demand for T4)
- Drug-induced goiter (lithium, sulfonamides, and phenylbutazone)
3) Genetic factors
- Dyshormogenetic goiter (where there is an inherited enzymatic defect that interferes with the synthesis of the thyroid hormone)
What are the different types of goiter?
1) Simple
- Diffuse and non-toxic
2) Multinodular
- Irregular enlargement of the thyroid due to recurrent episodes of hyperemia and involution
Describe the morphology of the diffuse goiter
1) Gross
- Diffuse goiter
- Symmetric enlargement
2) Microscopically
- Hyperplastic follicular epithelium that can pile up and form projections
- Involution, where the follicular epithelium becomes flattened and cuboidal with abundant colloid
Describe the morphology of the multinodular goiter
1) Gross:
- Multiple nodules of varying sizes
- One lobe of the thyroid might be more involved
- One nodule may become prominent and appear as a solitary nodule
- Goiters may grow behind the sternum and clavicle producing an intrathoracic/plunging goiter
- A cut section will reveal nodules of varying sizes (colloid nodule/colloid cyst)
2) Microscopically:
- Multiple variable-sized non-capsulated nodules with variable number and size of follicles with a variable colloid separated by a fibrous septa
Summarize the multinodular goiter
- Multiple nodules grossly
- Microscopically also various shaped nodules, colloids, follicles and are not encapsulated (Non-capsulated is important because in the thyroid if you have papillae its cancer. If you have a capsule, it’s a tumor that can be malignant or benign)
What are the congenital diseases of the thyroid?
1) DiGeorge syndrome:
- Chromosomal disorder due to 22q11.2 deletion, due to the failure of the development of the 3rd and 4th pharyngeal pouch
2) Thyroglossal Duct (TGD) cyst
- Cystic lesion that is lined by the respiratory epithelium, with a midline swelling
3) Branchial cleft cyst
- Anterolateral neck mass in children and young adults
- Microscopically the cyst is lined by a squamous, columnar, ciliated epithelium with abundant lymphoid tissue
What are the different types of thyroid neoplasms?
1) Cold nodule
2) Warm nodule
3) Hot nodule (benign)