E2L28-29 Endocrine: Thyroid Pathoma

Question 1

Embryology: Where does the thyroid develop in the fetus and what two pathologies arise from this fact?

Answer 1

Thyroid develops near the tongue and has to migrate down to the location in the throat. Lingual Thyroid is the persistence of thyroid tissue at the base of the tongue. Thyroglossal duct cyst occurs when the thyroglossal duct fails to involute and becomes cystic. Presents as anterior neck mass.

Question 2

What are the two main effects of hyperthyroidism and what is the specific cause of these effects?

Answer 2

1) Increased basal metabolic rate caused by increased synthesis of Na-K-ATPase
2) Increased sympathetic activity from increased expression of Beta-1 receptors

Question 3

How does increased thyroid hormone affect blood cholesterol and sugar levels?

Answer 3

Low cholesterol

High blood sugar

Question 4

What is the cause of Grave’s disease and the classic presentation?

Answer 4

Autoantibodies that stimulate TSH receptor in the thyroid. Causes diffuse goiter and hyperthyroidism and exophthalmos and pretibial myxedema

Question 5

Explain how exophthalmos and pretibial myxedema develop in Grave’s disease.

Answer 5

Fibroblasts exist behind the eye and in the pretibial area that have TSH receptors. The autoantibody in Grave’s disease activates these fibroblasts to produce glycosaminoglycan and cause inflammation, fibrosis, and edema.

Question 6

What would be seen microscopically in the thyroid of grave’s disease?

Answer 6

Hypertrophied follicles, chronic inflammation, and scalloped colloid

Question 7

Lab findings in Grave’s

Answer 7

High free T4
Low TSH
Low cholesterol
High Blood glucose

Question 8

How is Grave’s disease treated?

Answer 8

Beta-blockers, thioamide (blocks TPO), radioiodine ablation

Question 9

What is the dreaded consequence of Grave’s?

Answer 9

Thyroid Storm–potentially fatal
Elevated catecholamines and massive hormone excess usually in response to stress
Presents as arrhythmia, hyperthermia, vomiting, hypovolemic shock
Treated with PTU (propylthiouracil), beta blockers, steroids

Question 10

Patient has an enlarged goiter with multiple nodules. What is a potential cause and progression of the disease?

Answer 10

Cause–iodine deficiency

Outcome: regions can become TSH independent causing hyperthyroidism

Question 11

Explain Cretinism

Answer 11

Hypothyroidism in neonates and infants
S/Sx: mental retardation, short stature, skeletal abnormalities, coarse facial features, enlarged tongue, umbilical hernia
Cause: maternal hypothyroidism early in pregnancy, thyroid agenesis, dyshormonogenetic goiter, iodine deficiency
Remember that thyroid hormone is needed for normal brain and skeletal development

Question 12

Neonate is found to have mental retardation, short stature, enlarged tongue and umbilical hernia and coarse facial features. Diagnosis?

Answer 12

Cretinism

Question 13

Young adult presents with constipation, slowing of mental activity, muscle weakness, cold intolerance, weight gain despite normal appetite, deepening of the voice, and a large tongue. Diagnosis? Causes? Why the dee voice and large tongue?

Answer 13

All signs of Myxedema=hypothyroidism in older children and adults
Common causes are iodine deficiency, Hashimoto thyroiditis, lithium, surgical removal, radioablation
Deepened voice and large tongue come from deposition of glycosaminoglycans in the skin and soft tissue (myxedema)

Question 14

Patient describes Sx consistent with a period of hyperthyroidism followed by hypothyroidism. Diagnosis? Cause? Classic findings on histo? Blood markers? Potential complication late in the disease?

Answer 14

Hashimoto Thyroiditis
Autoimmune destruction of the thyroid assoc. with HLA-DR5
As the follicles are destroyed they initially release an increase in hormone followed by a decrease.
Antithyroglobulin and antithyroid peroxidase antibodies are often present as markers of the disease
Histo: chronic inflammation, germinal centers and Hurthle cells (eosinophilic metaplasia of cells lining follicles)
An enlarging thyroid gland late in disease is a B-cell lymphoma that is a potential complication of the disease.

Question 15

Patient presents with a tender thyroid following a viral infection. Diagnosis and outlook?

Answer 15

Subacute Granulomatous Thyroiditis (De Quervain)
Granulomatous inflammation that often follows a viral infection
Causes tender thyroid and transient hyperthyroidism
Self-limited, but rarely may progress to hypothyroidism

Question 16

Patient presents with a non-tender thyroid that is as hard as wood. Diagnosis?

Answer 16

Reidel Fibrosing Thyroiditis
Chronic inflammation with extensive fibrosis of the thyroid gland
Hypothyroidism
Fibrosis can involve local structures like the airway
Mimics anaplastic carcinoma except these patients are younger (40’s)