The Thyroid Gland (Chapter 14)

The two lobes of the thyroid are on each side of the ____

Trachea

Parathyroid glands are posterior to:

Thyroid

What is the primary function of parathyroid glands

Regulates serum calcium levels

What is an essential component of thyroid hormones?

Iodine

Thyroid hormone

• Produced by follicular cells of the thyroid

• Regulates metabolism, growth, energy use & neurologic development (especially critical in infants and children)

Calcitonin is produced by

Parafollicular C-cells of the thyroid

Calcitonin helps regulate:

Calcium homeostasis by lowering blood calcium (opposes parathyroid hormone)

Intake of ___ mcg of iodine leads to hypothyroidism

<50

What is the site of thyroid hormone synthesis?

Thyroid follicles

What are the two forms of thyroid hormones?

• Triiodothyronine (T₃)

• Tetraiodothyronine (T₄ or just thyroxine)

Thyroxine-binding globulin (TBG)

Primary transporter of T3 and T4

Thyroxine-binding prealbumin (TBPA)

Mainly binds to T4

Albumin

Most abundant protein in bloodstream; carries 10-15% of T3 and T4

Hypothalamic-pituitary-thyroid axis regulates:

Thyroid hormone production

Hypothalamus releases:

• Thyrotropin-releasing hormones (TRH)

• TRH acts on anterior pituitary

Anterior pituitary releases:

Thyroid-stimulating hormones (TSH)

Thyroid gland produces:

T3 and T4

Free T4 circulates in the bloodstream; when needed, it enters cells and is _____ into T3

Deionated

Thyrotoxicosis

General term; increased thyroid hormones from ANY cause

Hyperthyroidism

Excess thyroid hormones specifically due to overactive thyroid gland (overproduction)

Thyroglobulin

Storage form of thyroid hormones in the thyroid follicles

What is the most useful for thyroid evaluation?

Thyroid Panels, TSH in particular

More than 99.9% of thyroid hormone is ____

Protein bound

Thyroglobulin as an ideal:

Tumor marker thyroid cancer post-treatment surveillance

What is the most common cause of hyperthyroidism?

Graves` disease

The antibody; thyroid-stimulating immunoglobulin (TSI) binds to:

TSH receptors

The antibody; Thyroid-stimulating immunoglobulin (TSI) has what kind of effects on the thyroid?

• Stimulates thyroid gland growth 

• Increases thyroid hormone production (increase in T3 and T4)

Hashimoto’s Thyroiditis

An autoimmune disorder that causes the gradual destruction of thyroid gland and decreased hormone production

What antibodies are associated with Hashimoto’s thyroiditis?

Anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin

Hypothyroidism

Low Free T4 with normal or high TSH

What is one of the most common thyroid disorders?

Hypothyroidism

Hypothyroidism occurs in

5-15% of women >65 years old

What complications can hypothyroidism cause?

• Hyponatremia

• Anemia

• Hyperlipidemia

Primary hypothyroidism

Thyroid gland dysfunction

Secondary hypothyroidism

Pituitary dysfunction (low TSH)

Tertiary hypothyroidism

Hypothalamic dysfunction (low TRH)

What is the most common cause of thyrotoxicosis?

Graves` disease

Graves` Disease

Autoimmune disease in which antibodies are produced that activate TSH receptors

___ of patients with Graves` diseases have close relatives with this condition

15%

Who is more likely to develop Graves` disease?

Women 5x more likely to

Lab testing for Graves` disease shows:

High free T4 and/or T3 level with undetectable TSH

What symptom is associated with Graves` disease

Opthalmopathy (eye symptoms)

Toxic Adenoma and Multinodular Goiters are caused by:

Malfunctioning thyroid tissue (“out of control”)

In toxic adenoma/Multinodular goiters, the thyroid produces:

T3/T4 without TSH or TSH receptor-stimulating immunoglobulin

Toxic Adenoma and Multinodular Goiters are associated with:

TSH receptor mutations located in “toxic nodules” of the thyroid gland

Amiodarone

Medication used to treat cardiac arrhythmias

When iodine is given in large doses, effects are:

• Inhibiting of thyroid hormone production

• Blocking of T4 and T3 conversion

What condition is occurs when too much iodine is consumed or taken?

Amiodarone-Induced Thyroid Disease

Subacute Thyroiditis

Inflammation of the thyroid gland

Subacute Thyroiditis is characterized by:

Temporary changes in thyroid hormone levels

What are the three classifications of Subacute Thyroiditis?

• Postpartum

• Painless

• Painful