Thyroid glands are basically responsible to produce hormones and these hormones are control the whole body metabolism. Every person wants to know about thyroid glands. It is found in base of neck basically its shaped resembled like butterfly. Thyroid hormones are responsible to generate many function in body like whole body metabolism in which include breathing body weight, body temperature, muscular system, heart rate etc. If Thyroid disease could not control its swear condition leads to Thyroid carcinoma. In past its detection was not possible at early stage. Know a days miRNA Biomarkers are used to detect this carcinoma at early stage.

Table of Contents

Definition of Hormones

A product of living cells that circulates in body fluids (such as blood) or sap and produces a specific often stimulatory effect on the activity of cells usually remote from its point of origin; also : a synthetic substance that acts like a hormone. [1]

Hormones Definition from Biology perspective

Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Many hormones are secreted by special glands, such as thyroid hormone produced by the thyroid gland. [2]

Which of the glands secretes releasing hormones?

Thyroid hormones are basically tyrosine based hormones that are produced from thyroid glands that are responsible for metabolism regulation. T3 and T4 composed of iodine and deficiency of iodine leads to disease named as goiter. Doctors suggest Thyroid hormones tests to analysis various changing and blood health. The major form of thyroid hormone in blood is T4 blood test.

Its half-life is longer than T3 blood testing.  To evaluate disease different test are perfumed. Single thyroid function test not absolute diagnose of this disease and must be careful while select any test so their combination give comprehensive data that would enhance the diagnostic accuracy. Thyroid hormones Test helps measuring blood levels of hormones that makes easier to diagnose thyroid disease.

Misconceptions about hormones

Often people confuses that are hormones protein?

Not at all but few of them including small peptide hormones are proteins. Proteins hormones are peptide hormones.

What is the purpose of the thyroid gland Test?

The main objective of these Thyroid Tests may be the following

Evaluate dieases

Status of Gland (Functional)

Features of Thyroid Glands (Anatomical)

Causes behind dysfunctions of Thyroid

List of Major Thyroid Hormones Tests

  • Serum PBI and BEI levels Test
  • Serum T4 level Test
  • Effective thyroxine ratio (ETR) Test
  • Serum T3 level Test
  • Thyroid Stimulating Hormone: Serum TSH levels Test
  • Plasma tyrosine value Test

Serum PBI and BEI levels Test

Protein bound iodine chemical function is used as a test for thyroid function for long time

Serum PBI and BEI Level Test benefits

Where iodine technique is not available this method is used.

It is indirect measure of thyroid hormone

Serum PBI and BEI Level Test Disadvantage

This method is time taking

It also measure non hormonal iodine and iodotyrosines.

Serum PBI and BEI levels Normal range

Its normal range is 4.0- 8.0 µg%

In case of hyperthyroidism value greater then µg%

In case of hypothyroidism value below then 3 µg%

In case of normal value should be in between 4- 5 µg%

Precaution and Limitation in Serum PBI and BEI Level Test

To avoid any type of contamination precaution has to be taken

To avoid exogenous contamination all syringes and glass should be iodine free

Iodides iodine- containing contrast media and iodine containing drugs gives high level of false results in case of endogenous contamination.

Results also affected by traces elements. These chemicals interferes the iodine reduction reaction.

If serum TBG levels increase or decrease it also affects the results of test.

If serum TBG levels increase value will high if serum TBG levels low value will fall.

Serum TBG increased in case of


Oestrogen therapy

On oral contraceptive pills

Serum TBG decrease in case of

Hypoprotienaemic states

Nephrotic syndrome

Androgen therapy

Anabolic drug like diazole

Dicoumarol therapy

Inherited TBG deficiency

Serum T4 level Test

Most used methods are
RIA radioimmunoassay
Competitive protein binding assay (CPBA)

Serum T4 level Normal range

Its normal value is 4.0 – 11 µg%

In case of hyperthyroidism

More than 12 u µg%

In case of hypothyroidism

Less than 2.5 µg%

Effective thyroxine ratio (ETR) Test

In this era this is most effective method. This is more reliable method which can be readily carried out on the sample of serum it only required radioisotopy laboratory. Total serum thyroxine can be measured in to a single procedure and also binding capacity of thyroid hormone protein.

Serum T3 level Test

Most commonly RIA radioimmunoassay is used to measure T3 level. CPBA consider not a very good and accurate method to measure T3 levels due to less affinity of T3 for TBG.

Serum T3 level Normal range

Normal value is 100- 200 µg%

In females its value is slightly higher than males.

In hyperthyroidism

More than 350 µg%

In hypothyroidism

Less than 100 µg%

This method is effective for hyperthyroidism rather than hypothyroidism.

Test Price for T3 T4 Thyroid Stimulating Hormones

Average price range of the test is between Rs.0$ to Rs.400$ depending on the factors of city, quality & availability.

Thyroid Stimulating Hormone: Serum TSH levels Test

Radioimmunoassay technique is used. Measurement of serum TSH level is very sensitive index of thyroid hormone

Serum TSH levels Normal range

0 – 3 µu / ml average being 1.6 µ/ml

Plasma tyrosine value Test

Rivilin et al 1965 studied plasma tyrosine level in normal subject.


Plasma tyrosine value Normal value

It is 1.18 ± 0.4 µg/ml

In hyperthyroidism

Its value increase more than 70%.

How does hormone work – The Mechanism

In case of hyperthyroidism tyrosine transaminase inhibit due to the excess of thyroid hormones. In result of this catabolism of tyrosine inhibit and increase plasma tyrosine level. Authors wrote that hyperthyroidism is not due to age, sex, pregnancy or by previous iodides etc. they recommended tyrosine loading test for hyperthyroidism. They observed that plasma tyrosine level increase in case of hyperthyroidism by using tyrosine loading test.

In hypothyroidism

  • Plasma tyrosine level decrease in case of hypothyroidism.
  • List of hormones secreted by the hypothalamus
  • Thyrotropin-releasing hormone (TRH)
  • Gonadotropin-releasing hormone (GnRH)
  • Growth hormone-releasing hormone (GHRH)
  • Corticotropin-releasing hormone (CRH)
  • Somatostatin.
  • Dopamine.

List of Thyroid Hormones Tests Normal Ranges

Typical Ranges
Serum thyroxine
4.5-12 ug/dl
Serum Triiodothyronine
80-180 ng/dl
Serum thyrotropin
0.5-6 uU/ml
Serum thyroglobulin l
0-30 ng/m
Thyroid hormone binding ratio
Free Thyroxine index
Free Thyroxine
0.7-1.8 ng/dl
Free thyroxine fraction
Free Triiodothyronine l
230-619 pg/d
Free T3 Index
Radioactive iodine uptake

These and other blood test must be recommended by physicians. These are mandatory to diagnose thyroid disease, one can take these tests to check status but consult physician to start a proper medication.  This may cost a few dollars but can save hundreds of dollars you will need to pay after facing critical conditions.

Thyroid Tests based on primary function

Radioactive uptake studies

For thyroid gland iodine play very important role for its metabolism.  A trace element known as I 131 is used for the studies of thyroid function that is more convenient to use due to its shelf life. Other traces element like I132 and I 123 most commonly used in pregnant women as well as used in paediatric practice.

Normal range

Its normal value is 20 to 40 %

In Indian subjects its value is 15 to 30 %

Its value can very due to iodine intake person to person or population to population.

Serum PBI 131 (serum protein bound to iodine)

I131 accumulate in thyroid gland and appear as labeled hormone bound to protein it is a slow process. In case of hyperthyroidism level of protein bound radioactivity increase in plasma by scintillation method it can be measured accurately the result is conveniently expressed as conversion ratio which indicates the proportions of the total plasma radioactivity at 24 hrs.

Normal value

Its normal value is 35%

T3- suppression test

After 24 hrs radioactive iodine uptake studies and obtaining the basal value and serum T4 values, 20 ug of T3 four times daily given to & to 10 days

25 ug for 7 days 3 times in a day could be given alternatively.

RIU is repeated after T# administration and serum T4 values are also determined.


A suppression is indicated by the 24 hrs RIU falling to < 50 % of the initial uptake as (exogenous t3 suppression) TSH and total T4 to approx 2 ug / 100 ml or less.

On suppression indicates autonomous thyroid function.

TSH stimulation test

After 24 hours RIU studies 3 injection of TSH, each % USP units are given at 24 hours intervals

24 hours thyroidal RIU is measured after 42 hours after the final TSH dose


In case of primary hyperthyroidism there is failure of stimulation of thyroid gland

In secondary hyperthyroidism

There is stimulation of the gland showing increase RIU

TRH – Stimulation test

Tryptophan releasing hormone

With the availability of synthetic TRH –which is a tripeptied, suitable for human use, it is now possible to assess the functional integrity of thyrotrophic cells or the factors that influence the secretory response.


200 to 400 ug of TRH is administrated IV and blood samples at 0, 20, 40, and 60 minutes analysed for TSH content.


Peak response in normal is about 4 times elevation of TSH at 20 and $) minutes sample as compared to basal TSH level

In primary hypothyroidism or low levels hormnoes

The response will be exaggerated and prolong

In secondary hypothyroidism

The response will be blunted

In tertiary hypothyroidism

Hypothalamic in origin, increase in TSH is delayed

Test based on metabolic effects of thyroid hormones

BMR ( basal metabolic rate)

This test is help full to diagnose in case of severe condition


A BMR between 5 % to 20% consider normal


+50% – 70% found


-30% – 60% found

Serum cholesterol level

It is useful in case of hypothyroidism. Where its level become high


90% serum cholesterol level greater than 250 mg%

Serum creatine level

Its value remain between 0.6% to 1.6% (compared with BMR)

A normal serum creatine and normal BMR excludes thyroid dysfunction and held that when symptoms of thyroid disorders is present, raised serum creatine is highly significant even through BMR is normal.

Serum uric acid

Its value increase in myxoedematous male and postmenopausal women

It’s ranging from 6.5 to 11.0 mg %

Serum CK level

Serum CK level are often raised in hypothyroidism and also in thyrotoxic myopathy

How thyroid Gland works?

Working of thyroid gland is very important part of body because it is a part of endocrine system its working includes using iodine from food and utilizing it to generate body metabolism.

How endocrine system works?? It is very important question people ask

Endocrine system made up of glands which produced, store and release hormones in blood stream where these reached in to the body cell and maintain whole body metabolism.

These glands make to main hormones like

Triiodothyronine (T3)

Thyroxine (T4)

Production of T3 and T4?

T3 T4 Focus points

if T3 T4 level < high TSH and more thyroid hormones

if T3 T4 level > low TSH and less thyroid hormones

Basically two glands of brain hypothalamus and pituitary glands help to maintain levels of T3 and T4.working of pituitary gland and thyroid gland with each other.

Thyroid Disease States

How these diseases occur? Due to the low production or high production of hormones this disease occur and have effect on human health the two main types are found hypothyroidism and hyperthyroidism.


Hypothyroidism means deficiency of hormones. Due to the deficiency of iodine this disease occur this problem have been seen in those persons who are iodine deficient and due to the inflammatory disease of thyroid.

Hypothyroidism Symptoms

Common symptoms arises during childhood


Due to hypothyroidism lethargy occurs.

Sensitive toward cold

In case of hyperthyroidism patient is more sensitive toward cold. In case of chronic health problem condition is sever. In one of cause is hypothyroidism.


How hyperthyroidism effect on body? How fatigue occurs it’s very important to know many people who is affected due to thyroid disease they could not understand the cause of fatigue.

Fatigue occur due to the over activation of thyroid in some case it occur due to a lot of sleep and fatigue can result in case of hyperthyroidism may be insomnia, restless. It could be control due to its treatment by controlling overproduction of thyroid hormones.

Reproductive failure

Thyroid hormone have also effect on fertility hormones like estrogen and progesterone for normal function of ovary in case of hypothyroidism production balance of fertility hormones disturb which cause reproductive problem in females.

What is Myxedema?

If these signs are severe, the clinical condition is called myxedema.

Hyperthyroidism: Is it immune disease?

Hyperthyroidism is an immune disease in this disease autoantibodies bind and activate TSH receptors and stimulate thyroid hormones synthesis.

It is treated with anti-thyroid drugs

Symptoms of Hyperthyroidism


A person who has hyperthyroidism could not take proper sleep. Deficiency of sleeping is called insomnia

High heart rate

One of most common sign of this disorder is high heart rate. Reason is that due to the excess amount of thyroid hormone heart rate is high.  Symptoms are nervousness, palpitations etc.

Due to high heart rate heart beat leads to more than 100 beat per second. Which is abnormal heart beat.

Eye disease

Eye disease have you seen many people who have bulging eyes. This is due to the hyperthyroidism. Muscles and fatty tissues which are present behind the eyes they got inflamed that is way eye become red and swallow. This is also autoimmune disease.

Muscle weakness

Due to thyroid dysfunction body muscle becomes weak. Patient of hypothyroidism feel sever muscle weakens because of overproduction of thyroxine (thyroid hormones). A neuromuscular disorder known as thyrotoxic myopathy mostly found in patient of hyperthyroidism due to his muscle tissues breakdown.


Hifza is a student of bioinformatics. She is a research student and working on cancer.

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