Thyroid H Disorders

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Thyroid Hormone disorders


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Anatomy of the Thyroid Gland


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Thyroid gland Produces andSecretes 2 Metabolic Hormones

Two principal hormones

1-Tetraiodothyronine or Thyroxine (T4 )

2-triiodothyronine (T3)


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Thyroid-Stimulating Hormone(TSH)

Regulates thyroid hormone

production, secretion Is regulated by the negative feedback

action of T 4 and T 3


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Hypothalamic-Pituitary-Thyroid AxisNegative Feedback Mechanism


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Thyroid Hormone Action


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Thyroid Hormone Plays a Major Rolein Growth and Development

Thyroid hormone initiates or sustainsdifferentiation and growth

Essential for neural development andmaturation and function of the brain and CNS

Normal thyroid hormone function is importantfor reproductive function


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Clinical disorders1.Hyperfunction (hyperthyroidism)

A. Thyrotoxicosis: It results when tissues are exposed to

excessive levels of T4, T3, or both.

Causes

TSH-secreting pituitary tumors.


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Symptoms of thyrotoxicosis

Nervousness and anxiety

palpitations

Heat intolerance, hot and sweaty

loss of weight along with an increasedappetite

Scanty or irregular menses in women.


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B. Gravesdisease

It is an autoimmune condition. The serumcontains specific TSH immunoglobulins

(TSIs ) that bind to the TSH receptors on thefollicular cells of thyroid gland.

like natural TSH, stimulate the cells tosecrete thyroid hormone.


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Symptoms of Graves disease

Graves disease is manifested

by thyrotoxicosis symptoms(as before) and exophthalmos.


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Lab tests

1. An elevated 24-hour radioactive iodineuptake (RAIU) indicates true

hyperthyroidism.

2.Thyrotoxicosis ( TSH, T3, T4 )

3. In Graves disease ( TSH, T4,T3, TSIs )


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Treatment

1. Antithyroid drug ( PTU blocks thyroidhormone synthesis) .

2. Radioiodine therapy ( I 131 )

3. Surgical removal of the thyroid gland


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2 . Hypofunction (hypothyroidism )

Disorder in which the thyroid gland fails tosecrete an adequate amount of thyroid hormone.

May be primary or secondary

Causes 1.Chronic autoimmune thyroiditis (Hashimotosdisease)

2. Iatrogenic hypothyroidism

3. Iodine deficiency


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Signs and symptoms

a. In adult ( Myxedema) lethargy, fatigue ,

weakness and loss of

energy Decreased heart rate Cold intolerance Dry skin

Weight gain , Buffy faceand thickenedsubcutaneous tissue

Constipation Depression

Menestrual irregularities. physical and mental

sluggishness


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Buffy face-bags under theeyes


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Signs and symptoms

b. In children (Cretinism) Large size (despite poor

feeding habits) and increasedbirth weight

Puffy face and swollen tongue hoarse cry Low muscle tone Cold extremities

Persistent constipation Lack of energy, sleeping most

of the time

Little or no growth (dwarf) They are described as "good

babies"


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Signs and Symptoms

C- Simple Goiter

The thyroid gland is normal but is

unable to secrete thyroid hormones due

to deficiency of iodine in the diet .

Consequently, TSH is increased due to

-ve feedback mechanism, leading to

increased size of thyroid gland. It can

be best managed by administration of

iodine in diet.


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Lab tests

Thyroid function test: ( T3 ,T4 ,TSH )in adults.

Treatment Levothyroxine (L-thyroxine,T4) is the drug of

choice for thyroid hormone replacement .


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RULE

High TSH ------------- hypothyroidism

Low TSH ------------- hyperthyroidism


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THYROID HORMONECASES


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Questions

1- How could this case be diagnosed?

2- What type of treatment would yousuggest?


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CASE 2

A 27-year old female came to the clinic with a three-month history of heat intolerance, sweats, tremorsand severe muscle weakness which had limited herability to climb stairs. Her appetite had increased

remarkably despite weight loss. She was alsobothered by the pounding of her heart and someminor difficulty in swallowing. There was a positivefamily history of thyroid disease. She previously hadreceived iodide drops with improvement in hersymptoms but her disease recurred despitecontinued administration. Later, she stopped takingthe drops. Her other medical problems includediabetes which was controlled with diet and Lente

insulin.


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She had a history of non compliance with her clinic visits.Physical findings: -Blood pressure of 180/90 mmHg -Pulse of 110 beats/min.

-hypereflexia -Diffusely enlarged thyroid gland Lab values : TSH: 0.05 mU/L FT4: 3.1 ng/dl(N=0.7-1.9) After physical and laboratory investigations, the case was

diagnosed as thyrotoxicosis.


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Questions

1 - Mention the signs and symptoms suggestive forthyrotoxicosis?

2-Why were iodide drops initially effective inimproving the symptoms, but later ineffective? 3-When is iodide mainly indicated? This patient was started on PTU. One week later,

she complained that her symptoms were worseand the medication was not working. Sheadmitted missing doses because difficulty ofswallowing, cough and sore throat.


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4-PTU was ineffective in this case because : a- The patients non compliance

b- Prior iodide loading of the gland c- Slow onset of action of PTU d- a&b e- a&c

5- What may be the cause of patients complaints ofsore throat and cough? And What are the measurestaken for management of having sour throat andcough?


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LG is a 25-year-old pregnant woman whopresents with a history of anxiety, nervousness,and difficulty sleeping for the past 3 months.She complains of feeling hot and sweaty, andhas noticed her heart beating irregularly attimes during the day. Her eyes were prominentand stare. The case was diagnosed asHyperthyroidism.

CASE 3


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Canaris GJ, et al. Arch Intern Med. 2000;160:523-534.

Questions

1. What is the cause of LGs symptoms andwhat clues lead you to this conclusion?

2. What diagnostic tests would you order toconfirm her diagnosis? What would these testsshow?3- How could you treat this case?4- Is radioactive iodine contraindicated as adrug therapy during pregnancy? Why?


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A 19-year-old woman developssecondary amenorrhea followed bysymptoms of palpitations nervousness,heat intolerance and sweating. Apregnancy test is positive and T3 andT4 values are high.

CASE 4


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Canaris GJ, et al. Arch Intern Med. 2000;160:523-534.

Questions

1. What is the clinical picture of this case?

2. How could this case be managed as thepatient is probably pregnant?

3. Is radioactive iodine contraindicated asa drug therapy during pregnancy? Why?


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CASE 5

Elizabeth C., a child, was born at term weighing 7 lb.. The

mother's pregnancy had been normal but breast feeding was

not established and the infant was fed on National dried milk.

No abnormality was noticed by her parents until the onset of

vomiting, and difficulty in taking feeds at the age of 6 weeks.

When first examined at 8 weeks the infant's appearance

was suggestive of cretinism and there was enlargement of the

thyroid gland. When admitted to the hospital at the age of 4

months the features of cretinism were definite.


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Questions

1. Mention the cause and the main signs andsymptoms of cretinism?

2. How is cretinism treated?3. What is Pituitary dwarfism?4. What is the differencebetween cretinism and dwarfism?

Thyroid H Disorders

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