THE  THYROID  GLAND
This presentation is the property of its rightful owner.
Sponsored Links
1 / 34

THE THYROID GLAND PowerPoint PPT Presentation


  • 75 Views
  • Uploaded on
  • Presentation posted in: General

THE THYROID GLAND. HYPOTHYROIDISM. DIRECT METHODS Circulating levels of total hormones total thyroxine (TT 4 ) total triiodothyronine (TT 3 ) protein bound iodine (PBI) Circulating levels of free hormones free thyroxine (fT 4 ) free triiodothyronine (fT 3 )

Download Presentation

THE THYROID GLAND

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


The thyroid gland

THE THYROID GLAND

HYPOTHYROIDISM


Measurement of thyroid hormones

DIRECT METHODS

Circulating levels of total hormones

total thyroxine (TT4)

total triiodothyronine (TT3)

protein bound iodine (PBI)

Circulating levels of free hormones

free thyroxine (fT4)

free triiodothyronine (fT3)

Thyroid hormone binding proteins

Thyroxine binding globulin (TBG)

INDIRECT METHODS

Thyroid hormone binding tests

resin uptake of 125I-T3

Free thyroxine index (FTI)

FTI=

MEASUREMENT OF THYROID HORMONES

T4 x patient 125I-T3 resin uptake

Control 125I-T3 resin uptake


Other tests of thyroid function

Dynamic tests of thyroid activity

Thyroid uptake of 123I or 131I (and scan)

Thyroid uptake of 99mTc

T3 suppression test

TSH stmulation test

Tests of the thyroid-pituitary axis

Basal serum TSH

Serum TSH response to exogenous TRH

OTHER TESTS OF THYROID FUNCTION

exaggerated response - hypothyroid

normal response - euthyroid

impaired response - hyperthyroid


Hypothyroidism

HYPOTHYROIDISM

Hypothyroidism is a disease caused by a level of thyroid hormone insufficient for normal body function.

It affects every cell of human body.

An enlarged thyroid gland is the abnormality present in most cases.


Hypothyroidism1

HYPOTHYROIDISM

PRIMARY

/thyroid gland/

Causes of hypothyroidism

SECONDARY

/pituitary/

TERTIARY

/hypothalamus/


Primary hypothyroidism

CONGENITAL

Athyreosis

Ectopic thyroid

Dyshormonogenesis

Iodide deficiency

Antithyroid immunity

(transient due to illness)

ACQUIRED

Iodine deficiency

Autoimmunity

Post-radioactive iodine therapy

Post-thyroidectomy

Antithyroid drugs

(e.g. Carbimazole)

Iodine excess

Subacute thyroiditis

Thyroid irradiation

Primary hypothyroidism


Secondary hypothyroidism

Secondary hypothyroidism

pituitary tumours

pituitary granulomas (e.g. sarcoid) or injury

„empty sella” syndrome

Tertiary hypothyroidism

  • hypothalamic disorders (e.g. craniopharyngioma)

  • Isolated TRH deficiency


Causes of hypothyroidism

CAUSES OF HYPOTHYROIDISM

  • Iodine deficiency is the most common cause of goitre and bordeline hypothyroidism worldwide.

  • In noniodine-deficient areas autoimmunity is the common cause of hypothyroidism


Effects of iodine

EFFECTS OF IODINE

DEFICIENCY

Goitre, rarely hypothyroidism

EXCESS,

ACUTE

Temporary inhibition

of thyroid hormone synthesis

(Wolff-Chaikoff effect)

Induction of thyrotoxicosis

(Jod-Basedow phenomenon)

EXCESS,

CHRONIC

Goitre, hypothyroidism


Iodine deficiency

REDUCTION OF DIETARY IODINE INTAKE

 thyroid hormone production

(preferential secretion of T3 rather than T4)

compensatory  TSH secretion

IODINE DEFICIENCY


Iodine deficiency1

MODERATE

Urinary iodide excretion:

25 -50μ/g creatinine

Prevalence of goitre:

20 -50%

Hypothyroidism:

rarely

SEVERE

Urinary iodide excretion:

<25μ/g creatinine

Prevalence of goitre:

>50%

Hypothyroidism:

frequently

IODINE DEFICIENCY


Excess of iodine

EXCESS OF IODINE

Acute increase in intracellular iodine concentrations

Temporal inhibition of thyroid hormone synthesis and release

(Wolff-Chaikoff effect)

Decrease in intracellular iodine concentration

(escape from Wolff-Chaikoff effect)


Excess of iodine1

EXCESS OF IODINE

Introduction of iodine therapy in areas of iodine deficiency

Increase in the frequency of thyrotoxicosis

(Jod-Basedow phenomenon)

unmasking thyroid autonomy

(previously protected by iodine deficiency)


Excess of iodine2

EXCESS OF IODINE

Prolonged iodine ingestion in patients with autoimmune thyroiditis (Hashimoto’s disease) and in fetal and neonatal period (maternal ingestion of excess iodine)

Permanent hypothyroidism

and goitre formation

No excape from Wolff-Chaikoff effect


The thyroid gland

CLINICAL PICTURE OF HYPOTHYROIDISM DEPENDS ON TIME OF THE ONSET OF DISEASE


Congenital hypothyroidism

CONGENITAL HYPOTHYROIDISM

  • The prevalence:

    1 : ~4,000 live births

  • Usually no signs at birth

  • Untreated congenital hypothyroidism

    Non-reversible retardation of physical and mental development


Clinical features of congenital hypothyroidism

Typical face

Macroglossia

Enlarged posterior fontanelle (>0.5 cm) N

Hypotonia

Hypoactivity

Mottled skin

Cold extremities

Dry skin

Umbilical hernia (>0.5cm) N

Delayed passage of meconium N

Constipation

Feeding problems

Prolonged icterus N

Hoarse, grunting cry

Goiter

Placidity, lethargy

Growth retardation and immature body proportions

Mental retardation

Clinical features of congenital hypothyroidism

N – symptoms only observed in the neonatal period

All signs are facultative and frequently are not seen in the neonatal phase.


Congenital hypothyroidism1

CONGENITAL HYPOTHYROIDISM

  • May be detected biochemically by screening all neonates 3 – 5 days after birth.

T4 screening

TSH screening

Prematurity

Low TBG

Laboratory error

False positive

Laboratory error

Hypopituitarism

Laboratory error

Ectopic thyroid

Laboratory error

False negative


Acquired hypothyroidism

ACQUIRED HYPOTHYROIDISM

  • In noniodine-deficient areas

    primary hypothyroidism

    women : men = 10 : 1

  • The prevalence in women of all ages:

    2 - 4%

    (one-third of this cases  iatrogenic hypothyroidism)


Acquired hypothyroidism1

ACQUIRED HYPOTHYROIDISM

CLINICAL FEATURES IN HYPOTHYROIDISM

The symptoms of hypothyroidism are nonspecific and may be attributed by both patient and doctor to ageing, the onset usually being insidious.


Symptoms of hypothyroidism

USUAL

Lethargy

Increased sleep

Constipation

Mild weight gain

Cold intolerance

Facial puffiness

Dry skin

Hair loss

Hoarsensess

Abnormal menses

Acroparaesthesiae

Snoring

RARE

Deafness

Psychosis

Cerebellar disturbance

Myotonia

Symptoms of hypothyroidism


Signs of hypothyroidism

Change in appearance (e.g. face puffy and pale)

Periorbital oedema

Dry, flaking, cool, pasty skin

Diffuse hair loss

Bradycardia

Signs of median nerve compression

(carpal tunnel syndrome)

Effusions in body cavities

(e.g. ascites, pericardial effusion)

Delayed relaxation of reflexes

Croaky voice

Goitre

Rarely stupor or coma

SIGNS OF HYPOTHYROIDISM


Myxoedema

MYXOEDEMA

Myxoedema is a severe form of hypothyroidism causing complete exhaustion of all bodily functions.

All the organs are infiltrated with mucopolysaccharides that interfere with proper cell metabolism.

Myxoedema patients have all the symptoms and signs described for hypothyroidism, as well as low brain center reserve, low cardiac reserve, low respiratory reserve, low adrenal reserve, and low thermoregulatory reserve. In addition, they may show hyponatremia, hypercapnia, hypoxia, and anemia.


Hypothyroidism diagnostic procedures

HYPOTHYROIDISM- DIAGNOSTIC PROCEDURES

  • TSH level

    (second or third generation assays = the lower detection limit: 0.05-0.005 -0.002 mU/l)

  • FT4 level

    (the measurement of T3 is not a good diagnostic test for hypothyroidism)

  • TSH response to exogenous TRH

    (secondary and tertiary hypothyroidism; subclinical hypothyroidism)


Hypothyroidism summary of diagnostic tests

Primary

Hypothyroidism

Secondary

Hypothyroidism

Tertiary

Hypothyroidism

Non-thyroid

illness

Basal

TSH

raised

low or normal

low, normal

or elevated

normal or low

Hypothyroidism- summary of diagnostic tests

T4

low

low

low

low

TRH

response

exaggerated

reduced

or absent

sluggish

or delayed

normal or low


Subclinical hypothyroidism diminished thyroid reserve

Subclinical hypothyroidism(diminished thyroid reserve)

Serum T4 : normal (lower half of the normal range)

Serum T3: normal or sometimes even slightly elevated

Basal TSH: slightly raised

TSH/TRH: exaggerated

Definition: „subclinical”  no symptoms and signs (?)

Patients with subclinical hypothyroidism are at increased risk for coronary heart disease

HOWEVER


Imaging studies

IMAGING STUDIES

  • Rapidly growing large goiter;

  • Goiter with a dominant nodule;

  • Hashimoto’s disease

    ultrasonography examination and fine needle aspiration biopsy


Imaging studies1

IMAGING STUDIES

  • Cardiac function shoud be assessed before treatment is started.

  • The presence of other associated autoimmune endocrinopathies must be ascertained.


Hypothyroidism treatment

HYPOTHYROIDISM –TREATMENT

  • Hypothyroidismis treated with replacement T4 therapy (sodium L-thyroxine)

  • Replacement doses usually start at 50 μg/d being increased in a stepwise fashion at monthly intervals to 100 - 150 μg/d as the response is assessed clinically and biochemically.


Hypothyroidism treatment1

HYPOTHYROIDISM –TREATMENT

  • There is considerable variation in patient response to T4 because of differential thyroid hormone receptor isoform tissue concentration.


Hypothyroidism treatment2

HYPOTHYROIDISM –TREATMENT

During T4 therapy:

  • Serum T3 concentration must be in the normal range, as should that of TSH

  • Serum T4 may exceed the upper limit of normal.


Hypothyroidism treatment3

HYPOTHYROIDISM –TREATMENT

During T4 therapy:

  • Clinically satisfactory response:

  • normal pulse rate

  • and complete resolution of presenting symptoms and signs.

  • Occasionally cardiac symptoms such as palpitations may occur; in this case a β-adrenergic blocker drug is indicated.


Hypothyroidism treatment4

HYPOTHYROIDISM –TREATMENT

In patients with ischemic heart disease:

  • Replacement therapy should be introduced cautiously, with started doses of 25μg/d; increments should also be small.


Protocol for the management of myxoedema coma

Take blood for diagnostic tests: T4, TSH and plasma cortisol

Give 300 μg T4 i.v. and repeat approximately 100 μg q.d; give via nasogastric tube if i.v. preparation is unaviable

Treat hypothermia with gradual rewarming using blankets

Give i.m. hydrocortisone 75 mg immediately and repeat 25-50 mg 8-hourly

Give T3 20 μg i.v., i.m. or by nasogastric tube 12-hourly, if possible

Treat any heart failure with diuretics

Correct any electrolyte disturbances

Carefully exclude or treat infection

Use sedative drugs and fluids sparingly

Measure serum T4, T3 and TSH frequently

Protocol for the management of myxoedema coma


  • Login