Pathophysiology & Diagnosis of Thyroid Disease

Question 1

What laboratory results would be expected in a patient with secondary hyperthyroidism?

Answer 1

High TSH and T3/4, but low TRH due to negative feedback

Question 2

This thyroid disorder presents initially with hyperthyroidism followed by hypothyroidism.

Answer 2

Subacute (granulomatous) thyroiditis

Question 3

What is the most common cause of secondary hyperthyroidism?

Answer 3

TSH-secreting pituitary adenoma

Question 4

Describe the pathophysiology of Grave’s disease.

Answer 4

IgG autoantibodies bind and activate the TSH receptor on the thyroid leading to secretion of T3/4

Question 5

From what embryologic structure is the parathyroid derived?

Answer 5

4th pharyngeal pouch

Question 6

What is the most common symptoms causing patients with hyperthyroidism to seek care?

Answer 6

Proximal muscle weakness

Question 7

Thyroid hormones act synergistically to increase expression of what recetors?

Answer 7

Beta receptors - this is similar to the effect of catecholamines on beta receptors

Question 8

A patient presents with thyroid abnormalities. Serum TRH and TSH are low, but T3/4 are high. What is the diagnosis?

Answer 8

Primary hyperthyroidism

Question 9

What is the most common cause of primary hypothyroidism in the USA?

Answer 9

Hashimoto’s thyroiditis

Question 10

What is the effect of thyroid hormone on glucose levels?

Answer 10

Increases glucose levels via protein breakdown, lipolysis, and increases absorption in the gut

Question 11

These histocompatibility halotypes are associated with Grave’s disease.

Answer 11

HLA B8, DR3. DR2

Question 12

These cells are responsible for synthesizing and secreting calcitonin.

Answer 12

Parafollicular cells

Question 13

What is the most common cause of death in patients experiencing a thyroid crisis?

Answer 13

Cardiac arrhythmias

Question 14

Grave’s disease is what type hypersensitivity reaction?

Answer 14

Type 2 hypersensitivity

Question 15

This is the active form of thyroid hormone.

Answer 15

Tri-iodothyronine (T3)

Question 16

TRH stimulates release of TSH and thus thyroid hormone. What other hormone is released in response to high levels of TRH?

Answer 16

Prolactin - hyperprolactinemia is associated with primary hypothyroidism and the reason for associated hypogonadism

Question 17

This thyroid disorder is associated with signs of hyperthyroidism, painful thyroid, and recent history or a viral URT infection.

Answer 17

Granulomatous Subacute Thyroiditis

Question 18

True/False. T3 has a longer half life than T4.

Answer 18

False - T3 is the active thyroid hormone, but has a much shorter half life

Question 19

How can subacute thyroiditis and lymphocytic subacute thyroiditis be differentiated?

Answer 19

With subacute thyroiditis, there is an elevated erythrocyte sedimentation rate. This is normal in patients with lymphocytic subacute thyroiditis

Question 20

This dermatological finding is specific to Grave’s disease.

Answer 20

Grave’s dermopathy - thickening of the skin over the shins and dorsum of the feet

Question 21

What is the Wolff-Chaikoff effect?

Answer 21

Describes the autoregulatory control exerted by the thyroid gland on thyroid hormone synthesis based on serum iodide levels

Question 22

In a patient with tertiary hyperthyroidism, TRH, TSH, and T3/4 levels are high. What is the cause?

Answer 22

Hypothalamic lesion or TRH-secreting tumor

Question 23

This molecule binds 70% of all circulating plasma hormone.

Answer 23

Thyroid-binding globulin (TBG)

Question 24

What lab results would be expected in a patient with secondary hypothyroidism?

Answer 24

Low TSH and T3/4, normal or elevated TRH

Question 25

What is the most common cause of primary hyperthyroidism?

Answer 25

Grave's disease