Thyroid Gland

Question 1

Thyroid Hormone Stimulatory Factors

Answer 1

TSH
Thyroid-Stimulating Immunoglobulins
Increased TBG levels

Question 2

Thyroid Hormone Inhibitory Factors

Answer 2

Iodide deficiency
Deiodinase deficiency
Wolff-Chaikoff Effect (excess iodide)
Perchlorate/Thiocynate
PTU
Decreased TBG

Question 3

Thyroid Hormone Metabolism Effects

Answer 3

Increased protein synthesis and degradation
Increased Na/K ATPase will increase BMR

Increased lipolysis

Increased glucose absorption, glycogenolysis and gluconeogenesis

Question 4

Thyroid Hormone Cardiovascular Effects

Answer 4

Increased Beta-1 Receptor and Na/K ATPase will increase cardiac output and heart rate
Indirect increase in heat production

Question 5

Thyroid Hormone Synthesis Steps

Answer 5

1) Iodide trapping
2) Formation of Thyroglobulin in Rough ER and Golgi
3) Pendrin transports iodide to lumen while PTO makes it into iodine
4) PTO facilitates TG iodinization
5) PTO facilitates conjugation of MIT/DIT into T3 and T4
6) TG complex pinocytosed into epithelium
7) Proteases break off T3/T4
8) Deiodinase recycles MIT/DIT and TG

Question 6

Thyroid Stimulating Hormone

Stimulation, Actions and Dysfunctions

Answer 6

Increased TRH
Decreased Thyroid Hormones (especially T3)

Major regulator of thyroid hormone release and thyroid growth

Associated with Graves disease, Thyroid Neoplasms, Hashimoto’s Thyroiditis and Goiters

Question 7

Wolff-Chaikoff Effect

Answer 7

Excessive iodide intake causes decreased TH synthesis

Question 8

Perchlorate/Thiocynate Effect

Answer 8

Blocks Na+/I- cotransporter to decrease TH synthesis

Question 9

PTU Effect

Answer 9

Blocks peroxidase (PTO) to decrease TH synthesis

Question 10

Graves’ Disease

Description and Presentation

Answer 10

Increased thyroid stimulating immunoglobulin levels causes increased TH and decreased TSH

Presents with hypermetabolism, sweating, increased heart rate, periorbital edema and exophthalmos (bulging eyes)

Question 11

Exogenous Thyroid Hormone Effects

Answer 11

Can cause hyperthyroidism and osteoporosis

Question 12

Hashimoto’s Thyroiditis

Cause and Effects

Answer 12

Caused by autoAbs to Thyroglobulin or TPO
Leads to decreased TH which increases TSH

Can present with goiter from increased TSH

Question 13

Cretinism

Cause and Effects

Answer 13

Caused by untreated postnatal hypothyroidism
From low iodide, impaired gland development or maternal anti-thyroid medications

Leads to feeding/respiratory issues, growth/mental retardation, jaundice and hypotonia

Question 14

Iodine Deficiency Effects

Answer 14

Causes decreased TH synthesis which leads to increased TSH which can cause goiter