THYROID GLAND DONT ERASE ATE KAT

8/7/2019 THYROID GLAND DONT ERASE ATE KAT

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THYROID GLANDPinzon, Anne Katlyn G.


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What is Thyroid Gland?1.ANATOMY (microscopic and gross)2. PHYSIOLOGY (functionof thyroid)

3. Abnormalities

4.Clinical manifestationof abnormalities

5. Managementand treatment


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Thyroid gland is controlled

by the hypothalamus andpituitary (anterior pituitary).

Thyroid gland gets its name

from the Greek word for

"shield", after the shape of

the related thyroid cartilage.

Most common problems of

the thyroid gland consist of

an over-active thyroid

gland, referred to ashyperthyroidism and an

under-active thyroid gland,

referred to as

hypothyroidism'.


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one of the largest endocrine glands in the body

Brownish-red in color and is highly vascularized

Location: Anterior lower neck extending fromthe level of 5th cervical vertebrae down to the 1st

thoracic by 2 elongated lateral lobes connected

by median isthmus (12-15mm) overlying 2nd-4th

tracheal rings

each lobe has 50-60mm long with the superiorpoles diverging laterally at the level of oblique

lines

lower pole diverge laterally at the level of 5th

tracheal cartilage

the average weight of thyroid is 2-3 grams inneonates and 18-60 grams inadults but

heavier in women. the gland enlarges during menstruation and

pregnancy.


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Right lobe is also known as lobus dexter while left lobe is lobus sinister

Thyroid gland is covered by a fibrous sheath called capsula glandulae thyroidea

The gland is covered anteriorly with infrahyoid muscles and laterally with thesternocleidomastoid muscles

between the 2 layers of capsule and on posterior side of lobes, there are on

each side 2 parathyroid glands

thyroid isthmus is variable in presence and size, and can encompass a

cranially extending pyramid lobe (lobus pyramidalis orprocessus

pyramidalis), remnant of the thyroglossal duct


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The thyroid is supplied witharterial blood from the

superior thyroid artery, and

inferior thyroid artery.

Sometimes by the thyroidima artery


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The venous blood is drained via

superior thyroid veins, draining in

the internal jugular vein, and viainferior thyroid veins, draining via

the plexus thyroideus imparin the

left brachiocephalic vein.

Lymphatic drainage passesfrequently the lateral deep cervical

lymph nodes and the pre- and

parathracheal lymph nodes.

The gland is supplied byparasympathetic nerve input from

the superior laryngeal nerve and

the recurrent laryngeal nerve.


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HISTOLOGY

FOLLICLES- absorb iodine from the blood for production of thyroid

hormones and also forStorage of iodine in thyroglubin.

25% of all bodys iodide ions are in thyroid gland

Inside there follicles, Colloid serve as a reservoir of materials for

thyroid hormones

Production

THYROID EPITHELIAL CELL (follicular cell)- secretes T3 and T4.

When gland is not secreting, the epithelial cells range from low

columnar to cuboidal.

When gland is active, epithelial cells become tall columnar cell

PARAFOLLICULAR (C-CELL)- scattered among follicular cell and

secretes CALCITONIN.


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PhysiologyThe production of thyroxine andtriiodothyronine is regulated by thyroid-

stimulating hormone (TSH), released by

the anterior pituitary. The thyroid and

thyrotpes form a negative feedback loop:

TSH production is suppressed when the T4

levels are high. The TSH production itselfis modulated by thyrotropin-releasing

hormone (TRH), which is produced by the

hypothalamus and secreted at an

increased rate in situations such as cold (in

which an accelerated metabolism would

generate more heat). TSH production isblunted by somatostatin (SRIH) or growth

hormone-inhibiting hormone (GHIH) , rising

levels of glucocorticoids and sex hormones

(estrogen and testosterone), and

excessively high blood iodide

concentration.


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primary function of the thyroid gland is production of

the hormones triidothyronine (T3), thyroxine (T4),and calcitonin.80% of the T4 is converted to T3 by peripheralorgans such as the liver, kidney and spleen.

T3 is several times more powerful than T4, which islargely a prohormone, perhaps four or even tentimes more activeIodine is captured with the "iodine trap" by the

hydrogen peroxide generated by the enzyme thyroidperoxidase(TPO)Thyroid hormones play a particularly crucial role inbrain maturation during fetal development.


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Hyperthyroidismor overactive thyroid, is the overproduction of the

thyroid hormones T3 and T4, and is most commonly

caused by the development ofGraves' disease

an autoimmune disease in which antibodies areproduced which stimulate the thyroid to secrete

excessive quantities of thyroid hormones.

The disease can result in the formation of a toxic goiter

as a result of thyroid growth in response to a lack of

negative feedback mechanisms. It presents with

symptoms such as a thyroid goitre, protruding eyes

(exophthalmoses), palpitations, excess sweating,

diarrhea, weight loss, muscle weakness and unusual

sensitivity to heat.


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Hypothyroidism is theunderproduction of the thyroid

hormones T3 and T4. Hypothyroid

disorders may occur as a result of

congenital thyroid abnormalities,

autoimmune disorders such asHashimoto's thyroiditis, iodine

insufficiency. The removal of the

thyroid following surgery to treat

severe hyperthyroidism. Typical

symptoms are abnormal weightgain, tiredness, baldness,

temperature intolerance (both heat

and cold), and palpitation


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Hashimoto's thyroiditis is an autoimmune disorder whereby the body's own

immune system reacts with the thyroid tissues. At the beginning, the gland

is overactive, and then becomes underactive as the gland is destroyed

resulting in too little thyroid hormone production orhypothyroidism.

Hashimoto's is most common in middle-age females and tend to run infamilies. Also more common in individuals with hashimoto's thyroiditis are

type 1 diabetes and celiac disease.

Postpartum thyroiditis occurs in some females following delivery. The

gland gets inflamed and the condition initially presents with over activity of

the gland followed by under activity. In some cases, the gland does recoverwith time and resume its functions.

Initial hyperthyroidism followed by hypothyroidism


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Cancers occur in the thyroid gland and are more

common in females. The thyroid cancer presents

as a painless mass in the neck. It is very unusual

for the thyroid cancers to present with symptoms,unless it has been neglected. One may be able

to feel a hard nodule in the neck. Diagnosis is

made using a needle biopsy and various

radiological studies.

Non-cancerous nodulesmay find the presence of small masses (nodules)

in the neck. The majority of these thyroid nodules

are benign (non cancerous). The presence of a

thyroid nodule does not mean one has thyroid

disease. Most thyroid nodules do not cause any

symptoms, and most are discovered on anincidental exam. Doctors usually perform a

needle aspiration biopsy of the thyroid to

determine the status of the nodules. If the nodule

is found to be non-cancerous, no other treatment

is required. If the nodule is suspicious then

surgery is recommended.


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Antithyroid medicines

work best if you have mild hyperthyroidism

first time you are being treated forGraves' disease

younger than 50

Thyroid gland is only swollen a little bit (small goiter).

Radioactive iodine

Grave disease

older than 50

Thyroid nodules(toxic multinodular goiter) that are releasing too

much thyroid hormone.

Radioactive iodine is not used if:

pregnant or you want to become pregnant within 6 months of

treatment.

breast-feeding.

Thyroiditis


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If you have symptoms fast heartbeat

TremorsSweating

Nervousness

dry eyes

you may take some additional medicines to treat those symptoms.

Surgery is not usually part of initial treatment. You may need surgery

if your thyroid gland is so big that you have a hard time swallowing or

breathing. Or you may need surgery if a single large thyroid nodule

is releasing too much thyroid hormone.

During and after treatment for hyperthyroidism, you will have regularblood tests to check your levels ofthyroid-stimulating hormone (TSH).

You will also have regularthyroid hormone tests to check your levels

of hormones called T4 and T3. These tests are a good way to know

how well your treatment is working.


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The purpose of treatment is to replace the thyroid hormone that is

lacking. Levothyroxine is the most commonly used medication.

Doctors will prescribe the lowest dose that effectively relieves

symptoms and brings the TSH level to a normal range. If you have

heart disease or you are older, your doctor may start with a very small

dose.

Myxedema coma is a medical emergency that occurs when the body's level of

thyroid hormones becomes extremely low. It is treated with intravenous thyroid

hormone replacement and steroid medications. Some patients may need

supportive therapy (oxygen, breathing assistance, fluid replacement) and

intensive-care nursing.


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Important things to remember when you are taking thyroid

hormone

Do NOT stop taking the medication when you feel better

Continue taking the medication exactly as directed by your

doctor.

Some dietary changes can change the way your body absorbsthe thyroid medicine.

Talk with your doctor if you are eating a lot of soy products or a

high-fiber diet.

Thyroid medicine works best on an empty stomach and when

taken 1 hour before any other medications.Do NOT take thyroid hormone with calcium, iron, multivitamins,

albumin hydroxide antacids, colestipol or other medicines that

bind bile acids, or fiber supplements.


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THYROID GLAND DONT ERASE ATE KAT

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