1. Follicular cells 2. Parafollicular cells

Thyroid Gland and Hormones Flashcards by Armani Yulong

Thyroid Gland is shaped like?

BUTTERFLY

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Thyroid gland consists of ____ lobes, namely: ___ and ____ ; Which are connected by narrow band?

2; TRACHEA and LARYNX; ISTHMUS

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How many weeks of gestation does thyroid gland begin to produce measurable amounts of hormone?

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T/F
Does thyroid hormone play an important role?

TRUE

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These hormones influence metabolic activity in the body

T3 and T4

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T/F
All thyroid hormones DO NOT NEED IODINE to be formed

FALSE; ALL THYROID HORMONES ARE FORMED BY THE PRESENCE OF IODINE

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Steps in regulation of Thyroid Gland

Iodide
Thyroid (oxidized)
combined with Tyrosine
Forms MIT and DIT
coupled with T3 and T4

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These are precursors or pro-hormones for the production of hormones.

MIT and DIT

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Fundamental structural unit of the thyroid
gland

FOLLICLES

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Follicles appear as ____; They are also shaped as _____; They rest in the _____ and rich in _____

tiny buds/ sacs; RING; basement membrane; GLYCOPROTEIN

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The apex of the follicular cells has

MICROVILLI

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2 Types of cells:

Follicular cells
Parafollicular cells

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Type of cell that secretes T3 and T4 hormones

Follicular cells

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T/F
Follicular cells produce some ACTIVE rT3 and rT4

FALSE; INACTIVE rT3 and rT4

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Follicular cells have precursors namely?

MIT and DIT

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Parafollicular cells is also known as

C cells

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Type of cell that produces calcitonin

Parafollicular cells/ C cells

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Physiologic Effects of Thyroid Hormones (6)

Growth maturation and Sexual development
Heat Production and Energy expenditure
Influence carbohydrate, protein, and lipid metabolism
Increase oxygen consumption.
Increase heart rate.
Increase blood volume.

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This acts as preformed matrix containing tyrosyl groups.

THYROGLOBULIN

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Thyroglobulin is stored in ____
It weighs about ____

follicular colloid of thyroid gland; 15-25 g

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Steps in stimulating Thyroid hormone

Hypothalamus
secretes TRH
stimulate anterior Pituitary
secretes TSH
stimulate Thyroid hormone

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T/F
Is there a Positive feedback on hypothalamus and pituitary gland

FALSE; NEGATIVE FEEDBACK

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It is the GRADUAL or SLOW decreasing release of hormones; narrow or maintain limits

NEGATIVE FEEDBACK

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Percentage of T4 and T3 that is thyroid origin

100% T4 and 20% T3

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Where is the 20% of T3 originates?

Enzymatically non-thyroidal tissues

What is Monodeionization?

T4 becoming T3

Classifications of Thyroid Glands

1. Hyperthyroidism 2. Hypothyroidism 3. Euthyroidism

Hyperthyroidism is the ____ of thyroid hormones

EXCESS/ INCREASED

2 types of Hyperthyroidism

1. Primary 2. Secondary

Primary Hyperthyroidism PROFILE and gland that is abnormal

Increased T3, T4 and Decreased TSH; THYROID

Secondary Hyperthyroidism PROFILE and gland that is abnormal

Increased TSH, Pre-T4; PITUITARY

It is due to pituitary destruction of pituitary adenoma

Secondary Hyperthyroidism

Hyperthyroidism is caused by: (7)

1. Graves’ disease – antibody present against TSH (antibody attacks TSH) 2. Toxic adenoma – exposure to agents causing abnormalities. 3. Toxic multinodular adenoma 4. Exogenous iodine and Iodine-containing drugs. 5. Ectopic thyroid tissue pituitary tumor 6. TSH secreting pituitary tumor 7. Thyroid cancer

Symptoms of Hyperthyroidism (6)

1. Heat intolerance 2. Tachycardia 3. Weight loss 4. Weakness 5. Emotional inability 6. Tremor

Conditions of Hyperthyroidism

1. Thyrotoxicosis 2. Thyroid Storm

A condition that is applied to a GROUP OF SYNDROMES caused by HIGH LEVELS OF FREE THYROID HORMONES in the circulation

THYROTOXICOSIS

Thyrotoxicosis PROFILE and is also known as:

TSH is low; FT₄ is normal but increased FT₃; Plummer's disease

A condition that is rare and is destructive or severe when ignored

THYROID STORM

Hypothyroidism is the ____ of thyroid hormones

DECREASED

Hypothyroidism is treated with

thyroid hormone replacement therapy or levothyroxine

Hypothyroidism is caused by: (7) PAPACAR

1. Pituitary/ hypothalamus 2. Atrophic hypothyroidism 3. Post-surgery 4. Autoimmune hypothyroidism/ Hashimoto’s 5. Congenital hypothyroidism 6. Anti-thyroid drug therapy 7. Radioactive therapy

3 types of Hypothyroidism

1. Primary 2. Secondary 3. Tertiary

Primary Hypothyroidism PROFILE and gland that is abnormal

decreased T3 and T4; Increased TSH; THYROID

Primary Hypothyroidism is caused by

destruction or ablation of thyroid gland

Other causes of Primary Hypothyroidism

Surgical removal of the gland Radiation exposure Drugs like LITHIUM

Secondary Hypothyroidism PROFILE and gland that is abnormal

decreased T3, T4, TSH; PITUITARY

Tertiary Hypothyroidism PROFILE and gland that is abnormal

decreased T3, T4, TSH and TRH; HYPOTHALAMUS

Due to hypothalamic disease

Tertiary Hypothyroidism

Euthyroidism is a problem in ____ which makes it ____

rT3; INCREASED

Euthyroidism is caused by: (3)

1. Presence of goiter 2. Thyroid adenoma 3. Thyroid carcinoma

Major component of thyroid hormone

IODINE

Major source of IODINE

DIET

Additional source of IODINE

DEIONIZATION

Conversion of thyroid hormones:

LIVER, KIDNEYS; T4 – T3

Hormones which THYROID DO NOT ENTER CELLS and is Biologically inert

Protein bound thyroid hormones

T/F Protein-bound thyroid hormones acts as RESERVOIR for circulating thyroid hormones

TRUE

Hormones that are a Physiologically active form of thyroid hormones and it readily enter cells; exert biological effects

Free thyroid hormones

REGULATES production and secretion of thyroid hormone

Hypothalamic-Pituitary-Thyroid axis or HPTA

MAIN THYROID HORMONE released from thyroid gland.

THYROXINE or Total T4

Reference range for THYROXINE or Total T4 is

5-12.5 ug/dL (adults)

Distribution of THYROXINE or Total T4

- 70% of T4: bound to thyroid binding globulin (TBG) - 20% of T4: bound to Transthyretin/Prealbumin. - 10% of T4: bound to albumin

Thyroid disorders and their relation to Total T4

1. Primary hypothyroidism 2. Hyperthyroidism 3. T4 thyrotoxicosis 4. Low T3 and low T4 syndrome

Primary hypothyroidism PROFILE in Total T4

decreased T4; increased TSH

Hyperthyroidism PROFILE in Total T4

increased T3 and T4; decreased TSH

T4 thyrotoxicosis PROFILE in Total T4

increased T4; normal serum T3

Low T3 and low T4 syndrome PROFILE in Total T4

decreased T3 and T4

Analytical method for THYROXINE or Total T4

IMMUNOASSAY (Ab reagent)

Reference Interval of Thyroxine/ Total T4

5-12.5 ug/dL (71-161 mmol/L)

A CLASSICAL METHOD of adjusting a total T4 measurement for ALTERATIONS in binding protein

T3 uptake test

Biologically active fraction of T4 in circulating blood

FREE THYROXINE/ Free T4

Thyroid disorders and their relation to FT4

- Hyperthyroidism: increased or high FT4 - Hypothyroidism: decreased or low FT4

Reference method of measurement for Free thyroxine/ Free T4 is

Equilibrium dialysis

Other methods of measurement for Free thyroxine/ Free T4

1. ULTRAFILTRATION 2. SYMMETRICAL dialysis 3. MASS SPECTROMETRY 4. IMMUNOASSAYS 5. FT4 INDEX

A free T4 method that uses PRESSURE to push the plasma sample through a dialysis membrane

ULTRAFILTRATION

A free T4 method that plasma is DIALYZED against itself, using a radioactive tracer added on one side to measure the rate of diffusion of FT4 which is proportional to its concentration.

SYMMETRICAL dialysis

A free T4 method that simultaneously measures FT4 and FT3.

MASS SPECTROMETRY

A free T4 method that is from total T4 and unbound T4 sites serum proteins

FT4 INDEX

MAJOR THYROID HORMONES

1. T3 2. rT3 3. T4

Also known as: 3,5,3’ triiodothyronine

T3 or TRIIODOTHYRONINE

Most active thyroid hormone

T3 or TRIIODOTHYRONINE

T/F T3 or triiodothyronine is MORE tightly bound to serum proteins than T4

FALSE; LESS

Greater proportion of T3 exists in 3 forms namely:

1. Free form 2. Diffusible state 3. Protein-bound

Production of T3 or TRIIODOTHYRONINE

80% – produced outside the thyroid (tissue) through the deionization process. 20% - formed within thyroid gland

The principal application of T3 or TRIIODOTHYRONINE

Diagnosis of T3 thyrotoxicosis

T/F FT4 is better indicator of recovery from hyperthyroidism

FALSE; T3 or TRIIODOTHYRONINE

T/F T3 or TRIIODOTHYRONINE can be used for Reoccurrence of thyroidism

TRUE

T/F FT4 is helpful in confirming diagnosis of hyperthyroidism

FALSE; T3 or TRIIODOTHYRONINE

An increase in the plasma level is the first abnormality seen in cases of

HYPERTHYROIDISM

Thyroid disorders and their relation to T3

1. T3 thyrotoxicosis 2. Hyperthyroidism 3. Hypothyroidism

Analytical Method for T3 or TRIIODOTHYRONINE

IMMUNOASSAYS

Reference Values for T3 or TRIIODOTHYRONINE

- 80-200 ng/dL or 1.2 – 3.1 nmol/L (adult) - 105 – 245 ng/dL or 1.8 – 3.8 nmol/L (children 1-14 yrs old) - 60-160 ng/dL or 0.92-2.46 nmol/L (neonates)

It is the MAJOR METABOLITE of THYRONINE and produced by deiodination of T4

rT3 or REVERSE TRIIODOTHYRONINE

It is the removal of 1 Iodine from the inner ring of T4 and the end-product of FT4 metabolism

rT3 or REVERSE TRIIODOTHYRONINE

T/F rT4 is used to assess borderline or conflicting laboratory results of thyroid hormones

FALSE; rT3 or REVERSE TRIIODOTHYRONINE

T/F rT3 identifies patients with Euthyroid sick syndrome (increased rT3)

TRUE

T/F rT3 is used to represent the product of T4 metabolism

TRUE

Also known as 3,5,3’5’ tetraiodothyronine

T4 or TETRAIODOTHYRONINE

Principal secretory product of thyroid

T4 or TETRAIODOTHYRONINE

T/F Does T4 level represents the organic iodine level present in circulation

TRUE

The amount of ____ is a good indicator of the thyroid secretory production rate

serum T4

Elevated thyroxine causes inhibition of _____ and vice versa.

BH secretion

Reference values for T4 or TETRAIODOTHYRONINE

- 5.5 -12.5 ug/dL or 71-161 nmol/L (adult) - 11.8 – 22.6 ug/dL or 152-292 nmol/L (newborn/ neonate)

Other Hormones in Thyroid Gland

1. Thyrotropin – releasing hormone (TRH) 2. Thyroid – stimulating hormone (TSH) 3. Thyroglobulin

Regulate their own production by feedback inhibition to synthesis of TRH and TSH in the hypothalamus and pituitary

TRH or Thyrotropin – releasing Hormone

TRH is a _____ derived from a large prepro-TRH molecule.

Modified tripeptide

TRH acts also on the production of other pituitary hormones, especially _____

PROLACTIN

This plays a significant role in the regulation of the TRH gene

LEPTIN

Synthesized in the anterior pituitary gland that controls the biosynthesis and release of thyroid hormones from thyroglobulin

TSH or Thyroid – stimulating hormone

Less bound to serum protein compared to T4

TSH

TSH is a ____ with ____ and ___ subunits

GLYCOPROTEIN; A and B

Subunit that has the same amino acid sequences as LH, FSH and hCG

A subunit

Subunit that carries the specific information to the binding receptors for expression of hormonal activities.

B subunit

It is regulated by the hypothalamus through TRH as well as negative feedback from the thyroid hormones

TSH

Most important test in determining thyroid dysfunction

TSH

Measured commonly by 3RD GENERATION ASSAY that can measure down to 0.005 mU/L

TSH

Thyroid Disorders and their relation to TSH

1. Hypothyroidism 2. Nonthyroidal Illness 3. Subclinical hyperthyroidism

Hypothyroidism disorder in TSH has 3 types:

1. Primary hypothyroidism 2. Secondary hypothyroidism 3. Subclinical hypothyroidism

Primary hypothyroidism PROFILE in TSH

TSH levels are markedly elevated

Secondary hypothyroidism PROFILE in TSH

TSH secretion is decreased

Subclinical hypothyroidism PROFILE in TSH

elevated TSH levels but with T4 and FT4 levels are within the reference interval/ normal

Nonthyroidal Illness PROFILE in TSH

TSH levels may be increased or decreased

Subclinical hyperthyroidism PROFILE in TSH

TSH levels are decreased with T4 and T3 levels within reference interval

Reference Interval for TSH

0.5-5 uIU/mL

TSH and free T3 for hyperthyroidism classes

1. T3 Thyrotoxicosis 2. T4 Thyrotoxicosis

Overproduction of T3 with normal to low-normal T4

T3 Thyrotoxicosis

Overproduction of T4 with normal to low-normal T3

T4 Thyrotoxicosis

Synthesized and secreted by the follicles.

THYROGLOBULIN

It reflects thyroid mass, thyroid injury, and TSH receptor stimulation.

THYROGLOBULIN

T/F Is THYROGLOBULIN useful in monitoring the course of thyroid disease or response to treatment

TRUE

T/F Is THYROGLOBULIN recommended in pre-operative identification of thyroid malignancy?

FALSE; NOT RECOMMENDED

Conditions of THYROGLOBULIN (3)

1. Grave’s disease 2. Thyroiditis 3. Nodular goiter

THYROID HORMONE BINDING PROTEINS

1. Thyroxine – binding globulin (TBG) 2. Thyroxine – binding prealbumin (Transthyretin) 3. Thyroxine – binding albumin (TBA)

Main serum carrier for T3 and T4

Thyroxine – binding globulin (TBG)

This thyroid hormone binding protein's measurement is helpful if serum T3 and T4 levels do not agree with other laboratory parameters of thyroid function or not compatible with clinical findings

Thyroxine – binding globulin (TBG)

Thyroxine – binding globulin (TBG) transports: T4: T3:

70-75% 80%

Thyroxine – binding prealbumin (Transthyretin) transports: T4: T3:

15-20%; NONE

Thyroxine – binding albumin (TBA) transports: T4: T3:

10%; 20%

An autoimmune thyroid disease causes cellular damage and alters thyroid gland function

THYROID AUTOANTIBODIES

3 thyroid autoantigens

1. TPO (thyroperoxidase) 2. Tg (thyroglobulin) 3. TSH receptor (TR)

A thyroid autoantigen that antibodies responsible in hypothyroidism in Hashimoto’s and atrophic thyroiditis

TPO (thyroperoxidase)

Also known as TRAbs or thyroid stimulating Ig or long-acting thyroid stimulators (LATS)

TSH receptor (TR)

TSH receptor (TR) in Grave's Disease

Ig induced goiter and hyperthyroidism

Drugs that INCREASE in Thyroid Autoantibodies (COH-5)

Clofibrate estrogens Oral contraceptives Heroin Methadone 5-fluororacil

Drugs that DECREASE in Thyroid Autoantibodies

Androgens Glucocorticoids

Genetic condition that INCREASE in Thyroid Autoantibodies

Acute or Chronic active hepatitis Pregnancy Idiopathic

Genetic condition that DECREASE in Thyroid Autoantibodies

Complete deficiency partial liver failure Malnutrition Nephrotic syndrome

Screening for thyroid disorders is recommended when a person reaches _____ and ____

35 YEARS OLD and every 5 YEARS thereafter

The MOST COMMON CAUSE of Thyrotoxicosis which is an autoimmune disease.

Graves’ Disease (Diffuse Toxic Goiter)

Graves’ Disease (Diffuse Toxic Goiter) occurs 6x more commonly in ____

WOMEN

Caused by CIRCULATING ANTIBODIES to the TSH receptor – STIMULATING and BLOCKING antibodies

Graves’ Disease (Diffuse Toxic Goiter)

Distinct features of Graves’ Disease

Exophthalmia (bulging eyes) Pretibial myxedema

Diagnostic test for Grave's Disease

TSH receptor antibody test or TR antibody test

The thyroid turns into a woody or stony-hard mass.

Riedel ‘s Thyroiditis

It shows no clinical symptoms but TSH levels are low, and FT₃ and FT₄ normal.

Subclinical Hyperthyroidism

Associated with neck pain, low-grade fever, and swings in thyroid function tests

Subacute Granulomatous/Sub acute Non-supprative Thyroiditis/De Quervain’s Thyroiditis (Painful Thyroiditis)

In Subacute Granulomatous/Sub acute Non-supprative Thyroiditis/De Quervain’s Thyroiditis (Painful Thyroiditis) when Thyroidal Peroxidase (TPO) antibodies are absent:

ESR and thyroglobulin levels are elevated.

The most common cause of primary hypothyroidism

Hashimoto’s Disease (Chronic Auto-Immune Thyroiditis)

Methods for testing Hashimoto’s Disease (Chronic Auto-Immune Thyroiditis) and its result

TPO antibody = (+) result TSH = increased

Describes the peculiar nonpitting swelling of the skin

Myxedema

In Myxedema the skin becomes infiltrated by

mucopolysaccharides

Myxedema that is a severe form of primary hyperthyroidism

Myxedema coma

Clinical features of Myxedema (WESDAP)

- “Puffy Face” - Weight gain - Slow speech - Eyebrows thinned - Dry and yellow skin - Anemia

Defects in the development or function of the gland.

Congenital Hypothyroidism/Cretinism

Congenital Hypothyroidism/Cretinism screening test and result

T₄ (decreased)

Congenital Hypothyroidism/Cretinism confirmatory test and result

TSH (decreased)

The most SPECIFIC and SENSITIVE TEST for diagnosing thyroid disease

TRH Stimulation Test (Thyrotropin Releasing Hormone)

TRH Stimulation Test (Thyrotropin Releasing Hormone) measures relationship between ____ and ____ secretions

TRH and TSH secretions

TRH Stimulation Test is used to differentiate ___ and ____ patients who both had undetectable TSH levels.

euthyroid and hyperthyroid

TRH Stimulation Test may also be helpful in the detection of _____

thyroid hormone resistance syndromes

Dose needed in TRH Stimulation Test

500 µg TRH by IV

TRH Stimulation Test is INCREASED in ____ and DECREASED in ____

Primary hyperthyroidism; Hyperthyroidism

The MOST IMPORTANT thyroid function test; BEST screening test

TSH Test

The MOST CLINICALLY SENSITIVE ASSAY for the detection of primary thyroid disorders

TSH Test

TSH Test helps in early detection of

hypothyroidism

TSH Test differentiate _____ from _____

primary hypothyroidism; secondary hypothyroidism

TSH Test is used to MONITOR and ADJUST ____

thyroid hormone replacement therapy

It is used to measure the ability of the thyroid gland to trap iodine

Radioactive Iodine Uptake (RAIU)

It is helpful in establishing the CAUSE of hyperthyroidism

Radioactive Iodine Uptake (RAIU)

- It is normally used as a POSTOPERATIVE MARKER of thyroid cancer. - It is used in MONITORING the course of METASTATIC or RECURRENCE of thyroid cancer.

Thyroglobulin (Tg) Assay

Thyroglobulin (Tg) Assay INCREASES levels in

- Untreated and metastatic differentiated thyroid cancer - Hyperthyroidism

Thyroglobulin (Tg) Assay DECREASES levels in

- Infants with goitorous hypothyroidism - Thyrotoxicosis factitia

Thyroglobulin (Tg) Assay reference values

- 3-42 ng/mL or µg/mL (Adult) - 38-48 ng/mL or µg/mL (Infant)

Thyroglobulin (Tg) Assay methods for testing

- double-antibody RIA, - ELISA, - IRMA - Immunochemiluminescent assay (ICMA)

- It is used to assess BORDERLINE or CONFLICTING laboratory results. - It identifies patients with EUTHYROID sick syndrome

Reverse T₃ (rT₃)

Reverse T₃ (rT₃) reference Value

38-44 ng/dL

It indirectly assesses the level of free T₄ in blood

Free Thyroxine Index (FT₄1 or T₇)

Free Thyroxine Index (FT₄1 or T₇) is based on the ____ of bound T₄ and FT₄.

equilibrium relationship

It is IMPORTANT in CORRECTING Euthyroid individuals

Free Thyroxine Index (FT₄1 or T₇)

Free Thyroxine Index (FT₄1 or T₇) is elevated and decreased in

hyperthyroidism; hypothyroidism

Reference method of Free Thyroxine Index (FT₄1 or T₇)

Equilibrium dialysis

Free Thyroxine Index (FT₄1 or T₇) reference value

4-12 %

Test used to DIFFERENTIATE drug-induced TSH elevation and hypothyroidism

FT4

The value of ___ is in confirming hyperthyroidism.

TT₃ or FT₃

Measures the NUMBER of AVAILABLE binding sites of the thyroxine-binding proteins, most notably TBG

T₃ Uptake Test

T/F T₃ uptake Test does measure the level of thyroid hormones in serum

FALSE; DOEST NOT

In T₃ uptake Test, ____ increases TBG while ___ depresses TBG

Estrogen; Androgen

T₃ Uptake Test INCREASED levels in (HEC)

- Hyperthyroidism - Euthyroid patients - Chronic liver disease

T₃ Uptake Test DECREASED levels in (4)

- Hypothyroidism - Oral contraceptives - Pregnancy - Acute hepatitis

T₃ Uptake Test reference value

25-35%

It is used to CONFIRM RESULTS of FT₃ or FT₄ or abnormalities in the relationship of the total thyroxine

Thyroxine Binding Globulin Test (TBG)

It is useful to distinguish between hyperthyroidism causing thyroxine levels and euthyrodism with increased binding by TBG and increased thyroxine

Thyroxine Binding Globulin Test (TBG)

___ and __ are dependent on the amount of TBG

Total serum T₃ and T₄

Thyroxine Binding Globulin Test (TBG) INCREASED levels in (3)

- Hypothyroidism - Pregnancy - Estrogen

Thyroxine Binding Globulin Test (TBG) DECREASED levels in (2)

- Anabolic steroids - Nephrosis

MOST ACCURATE TOOL in the evaluation of thyroid nodules

Fine-Needle Aspiration

Used to test patients with thyroid cancers for the PRESENCE of RESIDUAL or RECURRENT disease

Recombinant Human TSH

Method and Test in Recombinant Human TSH

1. Tanned Erythrocyte Hemagglutination Method 2. Serum Calcitonin Test

Recombinant Human TSH that is method for antithyroglobulin antibodies

Tanned Erythrocyte Hemagglutination Method

Recombinant Human TSH that is test for tumor marker for DETECTING RESIDUAL THYROID METASTATIC in medullary thyroid carcinoma (MTC)

Serum Calcitonin Test

Most common cause of hypothyroidism

Atrophic hypothyroidism

Decreased size or shrinkage of hypothalamus

Atrophic hypothyroidism

Thyroid Gland and Hormones Flashcards

(211 cards)