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Hypothyroidism

Hypothyroidism, Myxoedema coma, Myxoedema triad

Thyroid Gland
Myxedema and Severe Hypothyroidism
ECG and Hypothyroidism

Thyroid Gland

Hypothalamic pituitary adrenal axis, Thyrotropin releasing hormone (TRH), Thyroid stimulating hormone (TSH)

The thyroid gland (Glandula thyroidea) synthesizes thyroid hormones:

Thyroxine (T4)
Triiodothyronine (T3)
The T4:T3 ratio is approximately 20:1. Therefore, only the level of T4 is measured

Hypothalamic-pituitary axis:

The hypothalamus synthesizes TRH
TRH stimulates the pituitary gland, which synthesizes TSH
TSH stimulates the thyroid gland, which synthesizes hormones T4, T3
Synthesis operates on a feedback mechanism

Hypothyroidism

Laboratory levels of (T4, T3) are reduced
Metabolism of the body is inhibited, leading to:

Sinus bradycardia, hypothermia, fatigue, bradypsychism, obesity, constipation...

Myxedema and Severe Hypothyroidism

Increased TSH (in hypothyroidism) reduces the breakdown of cellular mucopolysaccharides, which osmotically attract water. This leads to waxy to mucoid edema in the skin, subcutaneously, and also in organs (including the heart)
Myxedema and Severe Hypothyroidism. Severe (peripheral) hypothyroidism is sometimes referred to as myxedema because it causes waxy and mucoid edema, which acts as an insulator on the heart
Myxedema Coma occurs in prolonged hypothyroidism, leading to extreme drowsiness, even coma, with hypothermia (< 30°C).
Myxedema Cardiomyopathy is myxedema affecting the heart. It leads to deformation of the heart and its dysfunction

ECG and Hypothyroidism

Hypothyroidism (main feature):

Sinus Bradycardia

In severe hypothyroidism, the myxedema triad occurs:

Sinus Bradycardia
Low QRS Voltage (myxedema acts as an insulator)
Wide Negative T Waves

Additional signs:

Sinus Bradycardia

Heart Rate: 35/min. (<60/min.)
Sinus Bradycardia is the main feature of hypothyroidism
In severe hypothyroidism, the myxedema triad occurs

Myxedema Coma

A 79-year-old patient was brought to the hospital in coma

Laboratory results showed extremely high TSH and low T4

Myxedema Triad:

Sinus Bradycardia (30/min.)
Low QRS Voltage, especially in limb leads (I, II, III, aVF, aVL, aVR)
Wide Negative T Waves (V1-V6)

ECG myxoedema coma after treatment, sinus rhythm, normal T waves

Myxedema Coma (After Treatment)

This is an ECG from the previous patient

The patient received treatment for hypothyroidism (intravenous T3, T4)

Heart rate has normalized (heart rate: 70/min.)
Negative T waves have disappeared (V1-6)
Low QRS voltage persists due to persistent cardiac myxedema

Severe Hypothyroidism

The patient had laboratory results showing high TSH and low T4
Myxedema Triad:

Tendency towards sinus bradycardia (heart rate: 60/min.)
Reduced QRS voltage in the limb leads (I, II, III, aVF, aVL, aVR)
Flat T waves

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers

Home /

Hypothyroidism

Hypothyroidism, Myxoedema coma, Myxoedema triad

Thyroid Gland
Myxedema and Severe Hypothyroidism
ECG and Hypothyroidism

Thyroid Gland

The thyroid gland (Glandula thyroidea) synthesizes thyroid hormones:

Thyroxine (T4)
Triiodothyronine (T3)
The T4:T3 ratio is approximately 20:1. Therefore, only the level of T4 is measured

Hypothalamic-pituitary axis:

The hypothalamus synthesizes TRH
TRH stimulates the pituitary gland, which synthesizes TSH
TSH stimulates the thyroid gland, which synthesizes hormones T4, T3
Synthesis operates on a feedback mechanism

Hypothyroidism

Laboratory levels of (T4, T3) are reduced
Metabolism of the body is inhibited, leading to:

Sinus bradycardia, hypothermia, fatigue, bradypsychism, obesity, constipation...

Myxedema and Severe Hypothyroidism

Increased TSH (in hypothyroidism) reduces the breakdown of cellular mucopolysaccharides, which osmotically attract water. This leads to waxy to mucoid edema in the skin, subcutaneously, and also in organs (including the heart)
Myxedema and Severe Hypothyroidism. Severe (peripheral) hypothyroidism is sometimes referred to as myxedema because it causes waxy and mucoid edema, which acts as an insulator on the heart
Myxedema Coma occurs in prolonged hypothyroidism, leading to extreme drowsiness, even coma, with hypothermia (< 30°C).
Myxedema Cardiomyopathy is myxedema affecting the heart. It leads to deformation of the heart and its dysfunction

ECG and Hypothyroidism

Hypothyroidism (main feature):

Sinus Bradycardia

In severe hypothyroidism, the myxedema triad occurs:

Sinus Bradycardia
Low QRS Voltage (myxedema acts as an insulator)
Wide Negative T Waves

Additional signs:

Sinus Bradycardia

Heart Rate: 35/min. (<60/min.)
Sinus Bradycardia is the main feature of hypothyroidism
In severe hypothyroidism, the myxedema triad occurs

Myxedema Coma

A 79-year-old patient was brought to the hospital in coma

Laboratory results showed extremely high TSH and low T4

Myxedema Triad:

Sinus Bradycardia (30/min.)
Low QRS Voltage, especially in limb leads (I, II, III, aVF, aVL, aVR)
Wide Negative T Waves (V1-V6)

Myxedema Coma (After Treatment)

This is an ECG from the previous patient

The patient received treatment for hypothyroidism (intravenous T3, T4)

Heart rate has normalized (heart rate: 70/min.)
Negative T waves have disappeared (V1-6)
Low QRS voltage persists due to persistent cardiac myxedema

Severe Hypothyroidism

The patient had laboratory results showing high TSH and low T4
Myxedema Triad:

Tendency towards sinus bradycardia (heart rate: 60/min.)
Reduced QRS voltage in the limb leads (I, II, III, aVF, aVL, aVR)
Flat T waves

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers