thyroid disorder

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Second largest endocrine gland in body,Small butterfly shaped gland located at base of neck below the sternocleidomastoid muscles

Thyroid is controlled by the hypothalmus

and pituitary

Weighs 18-60gms in adults,Histologically it is made up of follicular and parafollicular cells.

Introduction of thyrodgland

thyrod gland folicular cell

Stimulates & maintains metabolic processes

Produces thyroid hormones T3-triiodothyronine and T4-thyroxine

These hormones regulate metabolism & affect the growth and function of other systems in the body

Secretes calcitonin to lower serum calcium levels

Parathyroid gland secretes PTH to raise serum calcium levels

function

Metabolic stimulants of:

Neural and skeletal development

Oxygen consumption at rest

Stimulating bone turnover by increasing formation and resorption

Promoting chronitropic and ionotropic effects

Increasing number of catecholamine receptors in heart

Increasing production of RBC

Altering the metabolism of carbs, fats, and protein

Function cont……..

T3 (Triiodothyronine) & T4

(Tetraiodothyronine Stored in Follicles (round sacs) in the thyroid filled

with thyroglobulin, a thyroid protein. Dietary iodine enters follicles where they are stored as

T3 and T4

T4 is converted to T3 by peripheral organs such as kidney, liver, and spleen

T3 is 10x more active than T 4

Only 20% of total T3 is secreted by thyroid

Hormones: T3 & T4

T4-thyroxine contains 4 iodine atoms

It is a slow-acting pre-hormone

T4 takes 4 days to peak in blood

Half-life 7 days

Overall effects take 6 weeks

T3 is the active and faster-acting hormone

The immediate effects of T3 last 1-2 days

Half-life 1.5 days

Hormones: T4

T3 and T4 structure

Dietary Iodide is removed from the bloodstream by

means of an active pump

The pump can concentrate iodide in the follicular sacs at 350x greater than the blood concentration

Oxidation of iodide by thyroid peroxidase converts iodide iodine

Peripheral de-iodination of T4 to T3 is regulated by many factors including health, nutritional status, and other hormones

Iodine

TSH

TSH is a pituitary hormone

Controlled by TRH-thyrotropin releasing hormone from hypothalamus

Functions to stimulate thyroid hormone production

May enlarge thyroid (goiter) when under producing

Labs:

High TSH indicates low thyroid hormone= hypo

Low TSH indicates high thyroid hormone = hyper

Hormones- TSH

Produced by thyroid to regulate serum calcium

levels

Calcitonin stimulates movement of calcium into bone

Parathyroid hormone (PTH) opposite effect of calcitonin

Hormones-Calcitonin & PTH

Negative Feedback System

TRH

T3 & T4 Thyroid

TSH

The disruption of any of these mechanisms can cause abnormal levels of T3 and T4 leading to thyroid disease

Primary Hypothyroidism

Disease of the thyroid gland

Secondary Hypothyroidism

Hypothalamic-pituitary diseases (reduced TSH)

Hypothyroidism

PRIMARY

Congenital Agenesis

Ectopic thyroid remnants

Defects of hormone synthesis Iodine deficiency

Dyshormonogenesis

Antithyroid drugs

Other drugs (e.g. lithium, amiodarone, interferon)

Causes of Hypothyroidism

Autoimmune Atrophic thyroiditis

Hashimoto's thyroiditis

Postpartum thyroiditis

Infective Post-subacute thyroiditis

Causes of Hypothyroidism

Iatrogenic Radioactive iodine therapy External neck irradiation post-surgery

Infiltration amyloidosis, sarcoidosis, hemochromatosis,

scleroderma

Causes of Hypothyroidism

SECONDARY

Hypopituitarism: tumors, pituitary surgery or irradiation, infiltrative disorders, Sheehan's syndrome, trauma, genetic forms of combined pituitary hormone deficiencies

Isolated TSH deficiency or inactivity

Hypothalamic disease: tumors, trauma, infiltrative disorders, idiopathic

Although anyone can develop hypothyroidism, you're at an increased risk if you:

Are a woman older than age 60 Have an autoimmune disease Have a close relative, such as a parent or grandparent, with an

autoimmune disease Have been treated with radioactive iodine or anti-thyroid

medications Received radiation to your neck or upper chest Have had thyroid surgery (partial thyroidectomy) Have been pregnant or delivered a baby within the past six

months

Risk factor

Fatigue Increased sensitivity to cold Constipation Dry skin Unexplained weight gain Puffy face Hoarseness Muscle weakness Elevated blood cholesterol level Muscle aches, tenderness and stiffness Pain, stiffness or swelling in your joints Heavier than normal or irregular menstrual periods Thinning hair Slowed heart rate Depression Impaired memory

signs and symptom

Diagnosis of hypothyroidism is based on your

symptoms and the results of blood tests that measure the level of TSH and sometimes the level of the thyroid hormone thyroxine. A low level of thyroxineand high level of TSH indicate an underactive thyroid. That's because your pituitary produces more TSH in an effort to stimulate your thyroid gland into producing more thyroid hormone.

diagnosis

Replacement therapy with levothyroxine (thyroxine, i.e. T4) is given for life. In the young and fit, 100 - 150 μg daily is suitable.

thyroid function tests after at least 2 months on a steady dose

the aim is to restore T4 and TSH to well within the normal range

An annual thyroid function test is recommended .

Treatment

Excessive amounts of the hormone can cause side

effects, such as:

Increased appetite

Insomnia

Heart palpitations

Shakiness

Goiter. Constant stimulation of your thyroid to release

more hormones may cause the gland to become larger —a condition known as a goiter.

Heart problems. Hypothyroidism may also be associated with an increased risk of heart disease, primarily because high levels of low-density lipoprotein (LDL) cholesterol — the "bad" cholesterol — can occur in people with an underactive thyroid.

Mental health issues. Depression may occur early in hypothyroidism and may become more severe over time. Hypothyroidism can also cause slowed mental functioning.

Complication

Peripheral neuropathy. Long-term uncontrolled hypothyroidism can

cause damage to your peripheral nerves — the nerves that carry information from your brain and spinal cord to the rest of your body,

Myxedema. This rare, life-threatening condition is the result of long-term, undiagnosed hypothyroidism. Its signs and symptoms include intense cold intolerance and drowsiness followed by profound lethargy and unconsciousness.

Infertility. Low levels of thyroid hormone can interfere with ovulation, which impairs fertility.

Birth defects. Babies born to women with untreated thyroid disease may have a higher risk of birth defects than may babies born to healthy mothers. These children are also more prone to serious intellectual and developmental problems. Infants with untreated hypothyroidism present at birth are at risk of serious problems with both physical and mental development.

Hyperthyroidism - result of excessive thyroid

function

major etiologies of thyrotoxicosis are hyperthyroidism caused by Graves' disease, toxic MNG, and toxic adenomas

Hyperthyrodism

Common

Graves' disease (autoimmune)

Toxic multinodular goitre

Solitary toxic nodule/adenoma

Causes of hyperthyroidism

Graves' disease. Graves' disease, an autoimmune

disorder in which antibodies produced by your immune system stimulate your thyroid to produce too much T-4, is the most common cause of hyperthyroidism.

Hyperfunctioning thyroid nodules (toxic adenoma, toxic multinodular goiter, Plummer's disease). This form of hyperthyroidism occurs when one or more adenomas of your thyroid produce too much T-4. An adenoma is a part of the gland that has walled itself off from the rest of the gland, forming noncancerous (benign) lumps that may cause an enlargement of the thyroid. Not all adenomas produce excess T-4, and doctors aren't sure what causes some to begin producing too much hormone.

Reasons for too much thyroxine (T-4)

Thyroiditis. Sometimes your thyroid gland can

become inflamed for unknown reasons. The inflammation can cause excess thyroid hormone stored in the gland to leak into your bloodstream. One rare type of thyroiditis, known as subacutethyroiditis, causes pain in the thyroid gland. Other types are painless and may sometimes occur after pregnancy (postpartum thyroiditis).

Cont……

Hyperthyrodism

Clinical features: due to

Hypermetabolic state

Overactivity of sympathetic nervous system

Symptoms

Weight loss

Increased appetite

Irritability

Tremor

Goiter

Restlessness

Stiffness

Muscle weakness

Breathlessness

Palpitation

Heat intolerance

Excessive sweating

Itching

Thirst

Vomiting

Diarrhoea

Oligomenorrhoea

Loss of libido

Signs

Tremor Irritability Psychosis Tachycardia or atrial fibrillation Warm peripheries Systolic hypertension Cardiac failure Lid lag Proximal myopathy Proximal muscle wasting Onycholysis Palmar erythema

Medical history and physical exam. During the exam your doctor may try to detect a slight tremor in your fingers when they're extended, overactive reflexes, eye changes and warm, moist skin. Your doctor will also examine your thyroid gland as you swallow.

Blood tests. A diagnosis can be confirmed with blood tests that measure the levels of thyroxine and TSH in your blood. High levels of thyroxine and low or nonexistent amounts of TSH indicate an overactive thyroid.

diagnosis

Radioactive iodine uptake test. For this test, you take a

small, oral dose of radioactive iodine (radioiodine). Over time, the iodine collects in your thyroid gland because your thyroid uses iodine to manufacture hormones. You'll be checked after two, six or 24 hours — and sometimes after all three time periods — to determine how much iodine your thyroid gland has absorbed.

A high uptake of radioiodine indicates your thyroid gland is producing too much thyroxine. The most likely cause is either Graves' disease or hyperfunctioning nodules.

If blood tests indicate hyperthyroidism, your doctor may recommend one of the following tests to help determine why your thyroid is

overactive:

Thyroid scan. During this test, you'll have a

radioactive isotope injected into the vein on the inside of your elbow or sometimes into a vein in your hand. You then lie on a table with your head stretched backward while a special camera produces an image of your thyroid on a computer screen.

The time needed for the procedure may vary, depending on how long it takes the isotope to reach your thyroid gland. You may have some neck discomfort with this test, and you'll be exposed to a small amount of radiation.

Treatment

Antithyroid drugs:

1. Carbimazole.

2. Propylthiouracil.

These drugs inhibit the formation of thyroid hormones

common side effects - rash, urticaria, fever, and arthralgia

Rare but major side effects include hepatitis; an SLE-like syndrome; and, most important, agranulocytosis

Treatment

Radioactive iodine

RAI accumulates in the thyroid and destroys the gland by local radiation.

It takes several months to be fully effective.

Surgery:

subtotal thyroidectomy

Only in patient who have previously been rendered euthyroid.

Goiter

Goiter refers to an enlarged thyroid gland

Biosynthetic defects, iodine deficiency, autoimmune disease, and nodular diseases can each lead to goiter

diffuse nontoxic goiter - diffuse enlargement of the thyroid occurs in the absence of nodules and hyperthyroidism

Worldwide, diffuse goiter is most commonly caused by iodine deficiency and is termed endemic goiter

Congenital Thyroid Diseases

Agenesis /Aplasia

Hypoplasia

Accessory or aberrant thyroid glands

Thyroglossal duct cyst

Thyroglossal Duct Cyst

A thyroglossal duct cyst is a neck mass or lump that develops from cells and tissues remaining after the formation of the thyroid gland during embryonic development.

Children

Failure of regression

Neck, medial

Squamous or columnar lining

often appears after an upper respiratory infection when it enlarges and becomes painful.

Complications: inflammation,

sinus tracts

History: A 50 year old housewife complains of progressive

weight gain of 20 pounds in 1 year, fatigue, postural dizziness, loss of memory, slow speech, deepening of her voice, dry skin, constipation, and cold intolerance.

Physical examination: Vital signs include a temperature 96.8oF, pulse 58/minute and regular, BP 110/60. She is moderately obese and speaks slowly and has a puffy face, with pale, cool, dry, and thick skin. The thyroid gland is not palpable. The deep tendon reflex time is delayed.

Laboratory studies: CBC and differential WBC are normal. The serum T4 concentration is 3.8 ug/dl (N=4.5-12.5), the serum TSH is 1 uU/ml (N=0.2-3.5), and the serum cholesterol is 255 mg/dl (N<200)

Case with hypothyrodism

History: A 35 year old nurse complained of nervousness, mood

swings, weakness, and palpitations with exertion for the past 6 months. Recently, she noticed excessive sweating and wanted to sleep with fewer blankets than her husband. She used oral contraceptives and her menstrual periods were regular.

Physical examination: Pulse was 92/minute and BP was 130/60. She appeared anxious, with a smooth, warm, and moist skin, a fine tremor, a bounding cardiac apical impulse, and she couldn't rise from a deep knee bend without aid. Her thyroid was diffusely enlarged, soft, mobile, without nodularity and there was no lymphadenopathy. Her eyes were not prominent (proptotic) and she had no focal skin thickening.

Laboratory studies: Serum T4=15.6 ug/dl and serum T3=210 ng/dl.

Case with hyperthyrodism

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