Thyroid Gland and Thyroid Diseases

Flashcards covering Thyroid Hormones and their related diseases. Includes causes, symptoms, mechanisms and key facts.

What secretes Thyroid-Releasing Hormone?

Hypothalamic neurons

What cells have receptors for Thyroid-Releasing Hormone?

Anterior Pituitary Thyrotropes

What does TRH bind to on the cell membrane?

Receptors

Which gland sends TRH to the anterior pituitary?

Hypothalamus

What is the end result of the TRH Mechanism of Action?

Synthesis and secretion of TSH

What type of receptor does TRH bind to?

Seven-member G-protein coupled receptor

What is the first messenger in the Phospholipase C Second Messenger System?

TRH

In the Phospholipase C Second Messenger System, what replaces GDP to activate the G protein?

GTP

What does the activated G-protein bind to in the Phospholipase C Second Messenger System?

Phospholipase C

What does Phospholipase C split PIP2 into?

Diacylglycerol (DAG) and inositol triphosphate (IP3)

What does DAG activate?

Protein kinase enzyme

What does IP3 release from intercellular storage sites?

Ca2+

What does free intracellular Ca2+ bind with?

Calmodulin

What does Calmodulin stimulate?

Synthesis and secretion of TSH

What is the most important early effect of Thyroid-Stimulating Hormone (TSH)?

Proteolysis of thyroglobulin

What does proteolysis of thyroglobulin cause?

Release of T3 & T4

What effects of TSH take hours, days, and weeks?

Increase activity of iodide pump, Increase iodination of tyrosine, Increase size and secretory activity of thyroid follicular cells, Increase number of thyroid cells

What can the increase in size and number of thyroid follicular cells cause?

Goiter

What is the second messenger system of TSH?

cAMP

What does TSH bind to on the cell membrane?

Seven-member G-protein coupled receptor

In the cAMP Second Messenger System, what replaces GDP to activate the G protein?

GTP

What does the activated G-protein bind to in the cAMP Second Messenger System?

Adenylate cyclase

What does adenylate cyclase convert ATP into?

cAMP

What does Cyclic AMP (cAMP) activate?

Protein kinases

What does active protein kinase stimulate?

Thyroid hormone synthesis and secretion

What is hyperthyroidism?

Any condition that causes the thyroid gland to produce too much thyroid hormones

What are some causes of hyperthyroidism?

Graves' disease and Thyroid adenoma

What is another name for Graves' disease?

Toxic Goiter or Basedow’s disease

What is the most common cause of hyperthyroidism?

Graves’ Disease

What percentage of hyperthyroidism cases are accounted for by Graves' disease?

70%

What is the population ratio of women to men affected by Graves' disease?

4:1

What is the Etiology of Grave's Disease?

Autoimmune Disorder

What antibodies are produced in Graves' Disease?

Thyroid-stimulating immunoglobulin (TSI)

How do TSI's affect the thyroid gland?

Activate the thyroid gland to produce thyroid hormones

What stimulates the thyroid gland to secrete thyroid hormones for about 1 hour?

TSH

What stimulates the thyroid gland to secrete thyroid hormones for about 12 hours?

TSI/TSAb

In Graves' disease, what suppresses the release of TSH?

High levels of thyroid hormones

What lab results are typical for Graves' disease?

Low TSH with high thyroid hormones T3 and T4

What does thyroid tissue affected by a tumor secrete?

Large quantities of thyroid hormones

What is the influence of TSH on the thyroid tissue affected in thyroid adenoma?

There is little to no influence.

What lab results are typical for thyroid adenoma?

High levels of thyroid hormones and low levels of TSH

Which symptoms are the result of an abnormally high metabolic rate?

Symptoms of Hyperthyroidism

Name symptoms of Hyperthyroidism.

Nervousness, anxiety, irritability, fast irregular heartbeat, intolerance to heat, increased sweating, weight loss, increased bowel movements, muscle weakness, extreme fatigue, hand tremors, moist skin, fine brittle hair, changes in menstrual pattern, erectile dysfunction

What is Exophthalmos?

Protruding eyeballs

What autoimmune condition is Exophthalmos commonly seen with?

Graves’ disease

What can result from elevated upper eyelids in Exophthalmos?

Dry, irritated eyes, infection, and potential cornea damage

What is a goiter?

Enlarged thyroid gland

What is Hypothyroidism?

Any condition that causes the thyroid gland to produce too little thyroid hormones

Name Causes of Hypothyroidism.

Hashimoto’s thyroiditis, Endemic goiter, Idiopathic goiter, Cretinism, Myxedema

What is another name for Hashimoto’s thyroiditis?

Non-Toxic Goiter

What is Hashimoto Thyroiditis?

Inflammation of the thyroid gland

What type of thyroiditis is Hashimoto Thyroiditis?

Chronic lymphatic thyroiditis

What is the most common cause of hypothyroidism?

Hashimoto Thyroiditis

What is the population ratio of women to men affected by Hashimoto’s?

7-10:1

What is the Etiology of Hashimoto's Thyroiditis?

Autoimmune Disorder

What is the mechanism of Hashimoto’s?

Autoimmune conditions damages follicular cells

What may signs/symptoms cycle between in early manifestations of Hashimoto's?

Hypothyroidism and hyperthyroidism

What happens when thyroid cells are damaged?

Stored thyroid hormones are dumped into circulation.

What autoantibodies are made in Thyroiditis?

Thyroglobulin antibody (TGAb) and Thyroid peroxidase antibody (TPOAb)

What does destruction of thyroid follicles release in circulation?

Tg and peroxidase

What blood test results may be found in early diagnostic blood tests for Hashimoto's?

High levels of thyroglobulin antibody (TGAb), Mildly high levels of thyroid peroxidase antibody (TPOAb)

What blood test results are found in advanced Hashimoto's?

High levels of TSH, High levels of Thyroglobulin antibody (TGAB), High levels of Thyroid peroxidase antibody (TPOAB), and Low levels of thyroid hormones

What are the two causes of Endemic Colloid Goiter?

Deficiency of enzymes and Deficiency of iodides in the soil

Why is iodine needed to form thyroid hormones?

Thyroid cannot form thyroid hormones without iodine

What does TSH stimulate the thyroid to secrete in Endemic Colloid Goiter?

Large amounts of thyroglobulin colloid

What does the secretion of large amounts of thyroglobulin colloid cause?

The gland to grow larger and larger creating a goiter.

What does a deficient peroxidase system lead to?

Iodides are not oxidized to the iodine state

What does deficient coupling lead to?

Tyrosine in the thyroglobulin molecule are not properly iodinated

What does a deficiency of the deiodinase enzyme do?

Prevents recovery of iodine from the iodinated tyrosine that are not coupled

What is cretinism caused by?

Congenital lack of thyroid gland, failure of thyroid gland, and/or lack of iodine

When does the thyroid of a baby become active in utero?

~ 3 months

What is cretinism characterized by?

Failure of body growth and severe mental retardation (IQ < 25)

What does damage to the anterior pituitary gland cause?

Decreased TSH secretion → Hypothyroidism

What is Myxedema?

Most severe form of hypothyroidism

What happens to thyroid hormone produced in Myxedema?

Almost no thyroid hormone is produced

What are signs/symptoms of Myxedema?

Accumulation of mucopolysaccharides under skin, Swelling of face, Non-pitting edema, Bagginess under eyes, Goiter, Atherosclerosis

Name signs and symptoms of Hypothyroidism.

Fatigue, Drowsiness, Forgetfulness, Difficulty learning, Slow heart rate, Thinning hair, Dry skin, Puffy face, Constipation, Weight gain, Heavy menstrual flow, Increased frequency of miscarriages, Increased sensitivity to many medications, Intolerance to cold, Hoarseness, Muscle weakness, aches, tender & stiff, Joint pain, stiffness or swelling, Elevated cholesterol

Where are thyroid hormones produced?

Thyroid Follicular Cells

What molecules are released from proteolysis of of thyroglobulin?

T3 & T4

What is the function of the iodide pump?

Iodide Trapping

Is Graves' Disease more common in men or women?

Women

Thyroid Adenomas secrete what kind of hormones?

Thyroid Hormones

What typically causes Exophthalmos?

Autoimmune disorder separate from Hyperthyroidism

What does TSH stand for?

Thyroid Stimulating Hormone

A goiter is an enlargement of what gland?

Thyroid gland

Where does the swelling occur in Exophthalmos?

Retro-orbital tissues

Anxiety is a sign/symptom of what thyroid disorder?

Hyperthyroidism

Weight gain can be a symptom of what thyroid disorder?

Hypothyroidism

What thyroid disorder is also known as Chronic Lymphatic Thyroiditis?

Hashimotos

Thyroglobulin is a substrate for which element?

Iodine

A goiter in Colloid Goiter is from increase secretion of what colloid?

Thyroglobulin

What is the function of the deiodinase enzyme?

Recovery of iodine from the iodinated tyrosine that is not coupled

Iodine deficiency can occur in utero, or in early __ period, leading to cretinism

Prenatal

What is the name of the location holding the pituitary gland?

Sella Turcica

What accumulates under the skin in Myxedema?

Mucopolysaccharides

What is the affect of cold temperatures in patients with hypothyroidism?

Cold Intolerance

How many iodine molecules are in Triiodothyronine?

Three

True or False: Hyperthyroidism can increase bowel movements

True

What is another thyroid disorder that has a 4:1 ration of occurrence in women?

Graves Disease

The swelling of tissues behind the eyes in Exophthalmos can compress which cranial nerve?

Optic Nerve