Thyroid Disorders

Question 1

What is the most common cause of hypothyroidism and what is the target of attack?

Answer 1

Hashimoto’s thyroiditis (Chronic Lymphocytic Thyroiditis)

TPO enzyme is the target of autoimmune attack

Question 2

What are some uncommon etiologies of hypothyroidism?

Answer 2

Iatrogenic: Thyroidectomy, Radioactive iodine (treatment of Graves’ disease)
Iodine deficiency (rare in North America)
Excess iodine load unmasking latent Hashimoto’s (ie. failure to overcome Wolff-Chaikoff effect)
Thionamides (used in treatment of hyperthyroidism to inhibit thyroid hormone synthesis, if dose too high)
Other drugs: Lithium, Interferon, Amiodarone
Thyroiditis (hypothyroidism usu transient)
Central hypothyroidism (pituitary disease)

Question 3

Who to screen for hypothyroidism?

Answer 3

Elderly (more prone to Apathetic Hypothyroidism)
Psychiatric disease
Pregnant women
Infertility
Hyponatremia

Question 4

What is the treatment for hypothyroidism?

Answer 4

L-T4 – levothyroxine (Synthroid or Eltroxin)

Question 5

What should you do if both adrenal insufficiency and hypothyroidism exists?

Answer 5

Replace glucocorticoids first to avoid precipitating adrenal crisis

Question 6

In relation to hypothyroidism, what situation would warrant from suppressing TSH levels rather than aiming for a normal level?

Answer 6

Thyroid cancer because TSH has growth promoting effects

Question 7

What is problematic about L-T4?

Answer 7

L-T4 is prone to reduced absorption by drugs, food, malabsorption, causing increased dose requirements
Calcium, Iron, Multivitamins, Antacids are notorious

Question 8

What is Myxedema Coma?

Answer 8

Severely decompensated hypothyroidism with progressive weakness, stupor, Bradycardia
Hypoventilation, Hypotension, heart failure, death
Hypoglycemia, hyponatremia, Hypothermia and has HIGH MORTALITY.

TSH extremely high, FT4 very low

Question 9

What are some precipitating factors to Myxedema Coma?

Answer 9

MI, CVA (cardivascular accident = stroke), infection

Question 10

What is the treatment for Myxedema Coma?

Answer 10

IV T4 (levothyroxine), Glucocorticoids, supportive care (ICU)

Question 11

What is thyrotoxicosis?

Answer 11

All causes of excess thyroid hormone, including exogenous, leakage of thyroid hormone

used interchangeably with hyperthyroidism

Question 12

What are some sign and sympyoms of thyrotoxicosis?

Answer 12

Increased basal metabolic rate: Sweating, heat intolerance, weight loss, increased appetite

Increased gut motility: Increased bowel movements, diarrhea

Increased cardiac: Palpitations, tachycardia, atrial fibrillation

Question 13

Please describe the broad categories of hyperthyroidism, their associated functional imaging result and treatment options

Answer 13

Excess thyroid hormone production, whereby part or all of gland has increased its hormone production
Functional imaging (thyroid scan or I-131 uptake) will show increased activity or uptake
Will respond to medication that inhibits thyroid hormone synthesis

Release of preformed stored hormone, or leakiness of the gland (AKA Thyroiditis)
There is no increased thyroid hormone synthesis, so functional imaging with show low or no uptake
No role for anti-thyroid meds

Exogenous thyroid hormone
Again functional imaging shows low uptake as no increased synthesis

Question 14

What are the causes of hyperthyroidism?

Answer 14

Excess Thyroid hormone Production
Diffuse: Graves’ disease
Nodule: Toxic adenoma; toxic multinodular goiter

Leakage of Stored Thyroid Hormone: Thyroiditis
Viral: Subacute thyroiditis
Autoimmune: Postpartum, silent

Exogenous thyroid hormone: Iatrogenic, factitious

Rare causes: TSH adenoma (central), metastatic thyroid cancer (follicular), struma ovarii (ectopic thyroid tissue in ovary)