Hypothyroidism Quiz: Test Your Knowledge of Low Thyroid Function

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Questions and Answers

What is the main function of the thyroid gland?

Control the balance of electrolytes in the body

Produce insulin to regulate blood sugar levels

Assist in the digestion of proteins

Secrete hormones to regulate metabolism (correct)

Which hormone is known as the most active thyroid hormone?

T3 (correct)

TRH

Thyroglobulin

Calcitonin

What is the role of calcitonin in the body?

Increase the amount of calcium in the blood

Regulate metabolism

Decrease the amount of calcium in the blood (correct)

Promote muscle growth

Where is thyroglobulin synthesized within the follicular cell?

Endoplasmic reticulum (ER) Signup and view all the answers

Which cells in the thyroid gland secrete calcitonin?

Parafollicular cells (C cells) Signup and view all the answers

What is the function of TRH (Thyrotropin releasing hormone) in thyroid hormone synthesis?

Stimulate the release of thyroid-stimulating hormone (TSH) Signup and view all the answers

How is iodide transported into the follicular cells from the blood?

Active transport Signup and view all the answers

What is the main function of TSH (Thyroid stimulating hormone) in thyroid hormone synthesis?

To bind to receptors on thyroid follicular cells Signup and view all the answers

Which organelle within the follicular cell is responsible for synthesizing thyroglobulin?

Endoplasmic reticulum (ER) Signup and view all the answers

What is the role of parafollicular cells (C cells) in thyroid function?

Produce calcitonin Signup and view all the answers

What is the basic unit of thyroid hormone T3?

3 iodine molecules attached to a tyrosine molecule Signup and view all the answers

What are the two main functions of thyroid peroxidase (TPO)?

Oxidation of iodide to iodine and coupling iodine with thyroglobulin Signup and view all the answers

What is the most common cause of primary hypothyroidism?

Autoimmune thyroid destruction (Hashimoto's thyroiditis) Signup and view all the answers

Which of the following is NOT a characteristic of Hashimoto's thyroiditis?

Permanent hypothyroidism that resolves without treatment Signup and view all the answers

What is the primary cause of Riedel's thyroiditis?

IgG4 antibody production leading to fibrous tissue formation Signup and view all the answers

What is the proposed mechanism behind DeQuervain's thyroiditis?

Viral upper respiratory tract infection leading to thyroid inflammation Signup and view all the answers

What is the underlying cause of the Wolff-Chaikoff effect?

Large ingestion of iodine inhibiting thyroid hormone production Signup and view all the answers

What is the primary distinguishing feature between primary and secondary hypothyroidism?

The level of TSH in the blood Signup and view all the answers

What is the underlying cause of Sheehan's syndrome?

Massive postpartum hemorrhage leading to pituitary necrosis Signup and view all the answers

Study Notes

Thyroid Gland

Largest endocrine gland, wraps around the front of the trachea
Consists of two lateral lobes connected by a median tissue mass (isthmus)
Composed of groups of thyroid follicles surrounded by connective tissue capsules
Follicles contain a space filled with glycoprotein colloid, enclosed by a layer of follicular cells

Thyroid Hormone Synthesis

Hypothalamus initiates synthesis of hormone, releasing TRH (Thyrotropin-releasing hormone)
TRH travels to the pituitary gland, stimulating the release of TSH (Thyroid-stimulating hormone)
TSH binds to receptors on thyroid follicular cells, stimulating the synthesis of thyroid hormones

Thyroid Hormones

Triiodothyronine (T3), the most active thyroid hormone
Thyroxine (T4), a precursor to T3
Calcitonin, produced by parafollicular cells (C cells), decreases blood calcium levels

Hypothyroidism

Two classifications: Primary and Secondary
Primary Hypothyroidism: destruction of the thyroid gland or iodine deficiency
Secondary Hypothyroidism: dysfunction of the hypothalamus and/or pituitary gland

Primary Hypothyroidism

Three main causes of thyroid destruction:
- Autoimmune thyroid destruction (Hashimoto's, Postpartum, Riedel's)
- Infectious thyroid destruction (DeQuervain's)
- Iatrogenic thyroid destruction (Thyroidectomy, Wolﬀ-Chaikoff Eﬀect)

Autoimmune Thyroid Destrution

Hashimoto's Thyroiditis: most common cause of hypothyroidism in the US
- Antibodies against thyroglobulin (anti-TG) and Thyroid Peroxidase (anti-TPO)
- Progressive depletion of thyroid epithelial cells due to autoimmune destruction
Postpartum Thyroiditis: transient hypothyroidism occurring within a year of childbirth
Riedel's Thyroiditis: characterized by developing fibrotic tissue at the thyroid gland

Infectious Thyroid Destrution

DeQuervain's Theory: rare, caused by viral upper respiratory tract infection
Painful thyroid goiter, elevated erythrocyte sedimentation rate (ESR)

Iatrogenic Thyroid Destrution

Thyroidectomy: recent thyroid surgery
Wolﬀ-Chaikoff Eﬀect: caused by large ingestion of iodine, inhibiting TPO and preventing thyroid hormone production

Secondary Hypothyroidism

Dysfunction of the hypothalamus and/or pituitary gland
Unable to produce TRH and/or TSH, resulting in low thyroid hormone production
Low T3 and T4, with low TSH (important for diagnosis)

Pituitary Dysfuncion

Pituitary adenoma: tumor on the pituitary gland
Sheehan Syndrome: postpartum hypopituitarism due to necrosis of the pituitary gland

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Description

Test your knowledge about hypothyroidism, a condition where the thyroid gland is underactive and produces low levels of T3 and T4 hormones. Learn about the structure and function of the thyroid gland, its hormone production, and its role as an endocrine organ.