THYROID

UNDERSTANDING THE THYROID PROBLEMS

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THE BASICS

HYPOTHYROIDISM,HYPERTHYROIDISM,

CANCERS

Thyroid :

• The Thyroid or Thyroid gland is one of the largest endocrine glands.
• It is found in the neck , below the thyroid cartillage(which forms the adam's apple or laryngeal prominence).
• The thyroid gland controls how quickly the body uses energy, makes proteins , and controls how sensitive the body is to other hormones.
• It participates in these processes by producing thyroid hormones .
• The principle ones being triiodothyronine and thyroxine which can sometimes referred as tetriaodothyronine .
• These hormones regulate the growth and function of many other systems in the body.
• (T3 & T4) are synthesized from iodine and tyrosine.
• The thyroid also produces calsitonin , which plays a role in calcium homeostatis.
• Hormonal output from the thyroid is regulated by thyroid - stimulating hormone (TSH) produced by anterior pituitary , which itself is regulated by thyrotropi - releasing homone (TRH) produced by hypothalamus.

Anatomy :

• The thyroid gland is butterfly shaped organ and is composed of two cone like lobes or wings ,Lobus dexter and lobus sinister, connected via isthamus.
• This organ is situated on the anterior side of neck, lying against the larynx and trachea , reaching posteriorly Oesophagus and cartiod sheath .
• It starts cranially at oblique line on thyoid cartillage (just below the adam's apple) and extends inferiorly to approximately to fifth or sixth tracheal ring ,
• It is difficult to demarcate , the glands upper and lower border with vertebral levels because it moves position in relation to these during swallowing .
• It is covered by thin fibrous sheath, the capsula glandulae thyroidia, composed of an internal and external layer.
• The external layer continuous with the pretracheal fascia and posteriorolaterally continuous with the cartiod sheath .

• This gland is covered with anteriorly with infrahyoid muscles and laterally with the sternocleidomastoid muscle also known as sternomastoid muscle .
• Between the two layers of the capsule on the posterior side of the lobes, there are on each side two parathyroid lobes .
• In a healthy person the gland is not visible yet can be palpated as a soft mass.
• Having the patient neck flex slightly to the side when being palpated may help in this examination.
• Thus when the patient swallows, the gland moves superiorly as does the whole larynx.
• The Thyroid is supplied with arterial blood from the superior thyroid artery a branch of external cartiod artery and the inferior thyroid artery.
• The venous blood is drained via superior thyroid veins , draining in the internal jugular vein and via inferior thyroid veins draining via the plexus thyroideus impar in the left bracheocephalic vein.
• Lymphatic drainage passed frequently the lateral deep cervical lymph nodes and the pre-parathracheal lymph nodes , 
• The gland is supplied by the parasymphathetic nerve input from the superior laryngeal nerve and the recurrent laryngeal nerve.

(T3 & T4) regulation :

• The production of thyroxine(T3) and triiodothyronine(T4) is regulated by thyoid - stimulating hormone (TSH), and released by the anterior pituitary.
• The thyroid and thyrotropes form a negative feedback loop;
• TSH production is suppressed , when the T4 levels are high.
• The TSH production itself is modulated by thytotropin - releasing hormone (TRH), which is produced by hypothalamus and screated at an increased rate in situations such as cold exposure .
• TSH production is blunted by stomatostatin(SRIH),and excessively high blood iodide concerntration.
• An additional hormone produced by the thyroid contributes to the regulation of blood calcium levels .
• parafollicular cells produce calcitonin in responce to hypercalcemia, 
• calcitonin stimultes movment of calcium into bone,in opposition to the effects of parathyroid hormone (PTH), however calcitonin seems far essential than PTH as calcium metabolism remains clinically normal after the removal of thyroid , but not the parathyroids.

DISORDERS

Hypothyroidism :

• It is the under production of thyroid hormones T3 &T4.
•  Hypothyroid diorders may occur as a result of 
• Congenital thyroid abnormalities (thyroid defeciency at birth).
• Autoimmune disorders , such as hashimoto's thyroiditis.
• Iodine defeciency (more likely in poorer countries ) or 
• The removal of thyroid following surgery to treat severe hypothyroidism and /thyroid cancer .

Typical symptoms are abnormal weight gain , tiredness, baldness , cold intolerence, and bradycardia .

• Hypothyroidism is treated with Hormone replacement theraphy such as levothyroxine.
• Negative feedback mechanisms result in growth of thyroid gland when thyroid hormones are being produced in sufficiently low quantities .
• as a means of increasing the thyroid output .
• However where the hypothyroidism is caused is caused by iodine insufficiency , the thyroid is unable to produce T3 & T4 and as a result the thyroid may continue to grow to form a non toxic goitor .
• It is termed non-toxic as it does not produce toxic quantities of thyroid hormones , despite its size.

Initial Hyperthyroidism followed by Hypothyroidism :

• This is the over production of T3 & T4 , there are two types
• Hashimoto's thyroiditis & postpartum thyroiditis.
• Hashimoto's disease is an autoimmune disorder, whereby the body's immune system reacts with thyroid tissues in an attempt to destroy it .
• At the beginning , the gland may be overactive, and then bcomes underactive as the gland is damaged resulting in too little thyoid hormone production or hypothyroidism.
• Also more common individuals with Hashimoto's thyroiditis are type 1 diabetes and celiac disease.
• Postpartum thyroiditis occurs in females following the birth of child,
• After child , the gland becomes inflammed and the condition initially presents with the overactivity of the gland followed by underactivity.
• The etiology is not always known , but can sometimes be attributed to autoimmunity such as Hashimoto's thyroiditis or grave's disease.

Cancers :

• In most cases, thyroid cancer presents as a painless mass in the neck .
• It is unusual for thyroid cancers to present with symptoms ,unless they have 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 nodules :

• Many individuals find the nodules in the neck .
• Doctors usually perform a needle aspiration biopsy of thyroid to determine the status of the nodules .
• If the nodule found to be non-cancerous and no other treatment is required.
•  If the nodule is suspecious then surgery is recommended.

Other disorders:

• Limited research shows that seasonal allergies may trigger episodes of hypo or hype-hyperthyroidism.
• An ectopic thyroid is an entire or parts of the thyroid located in another part of the body then what is the usual case.
• Same rapid cycling versions of bipolar disorder seem to have a complex relationship with thyroid disfunction, however the specifics of the relationship are poorly understood.

Preventive tips :

 A healthy diet, exercise, proper nutrition and stress reduction can all minimise the chance of developing thyroid disease.

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