HYPOTHYROIDISM Flashcards
What is hypothyroidism?
Hypothyroidism results from any disorder that leads to insufficient secretion of thyroid hormones from the thyroid gland.
Name the four causes of congenital hypothyroidism.
- Absent or under-developed thyroid gland<br></br>2. Dyshormogenesis - genetic defects in the synthesis of thyroid hormones, resulting in hypothyroidism with goitre<br></br>3. Iodine deficiency during pregnancy<br></br>4. Maternal transmission of antithyroid drugs
List three causes of primary hypothyroidism.
- Hashimoto’s thyroiditis<br></br>2. Iodine deficiency<br></br>3. Iatrogenic causes (e.g., post-ablative therapy, surgery)
What are the clinical features related to decreased metabolic rate in hypothyroidism?
Tiredness/malaise, weight gain, cold intolerance, decreased sweating, coarse, sparse hair, brittle nails, cold, dry skin, constipation, bradycardia, hypothyroid myopathy, delayed relaxation of deep tendon reflexes, hyperlipidemia (xanthelasmas), hypercarotenemia.
Define myxoedema and list symptoms related to generalised myxoedema in hypothyroidism.
Myxoedema refers to the accumulation of mucopolysaccharide in subcutaneous tissues. Symptoms include doughy skin texture, puffy appearance, myxoedematous heart disease, periorbital edema, pretibial myxoedema, entrapment syndromes, peripheral neuropathy, macroglossia, deep hoarse voice, myxoedema coma.
What is the most common cause of hypothyroidism in iodine-sufficient regions?
Hashimoto’s thyroiditis.
Name the thyroid antibodies associated with autoimmune hypothyroidism.
Anti-TPO antibody (95%), Anti-thyroglobulin (60%), TSH receptor antibody (blocking) (10-20%).
How is myxoedema coma managed?
Passively rewarm, cardiac monitoring for arrhythmias, close monitoring of urine output, fluid balance, central venous pressure, blood sugars, oxygenation, broad-spectrum antibiotics, thyroxine cautiously, hydrocortisone if adrenal failure.
What are the long-term complications of autoimmune hypothyroidism?
Increased risk of developing other autoimmune diseases and increased risk of developing B-cell NHL in the affected gland.
How is levothyroxine dosage adjusted in elderly patients with a history of ischemic heart disease?
Start levothyroxine at 25-50 µg daily and adjust every 4 weeks according to response.
In secondary hypothyroidism, what are the levels of TSH, Free T4, and T3?
TSH is low (or ‘normal’), and Free T4 and T3 are low.
Name three symptoms related to decreased metabolic rate in hypothyroidism.
- Tiredness/malaise<br></br>2. Weight gain, despite decreased appetite<br></br>3. Cold intolerance
What are the dermatological symptoms associated with hypothyroidism?
Coarse, sparse hair, brittle nails, cold, dry skin
What gastrointestinal symptoms are commonly seen in hypothyroidism?
Constipation
Describe the cardiovascular symptom associated with hypothyroidism.
Bradycardia - slow pulse
What is hypothyroid myopathy, and what are its symptoms?
Hypothyroid myopathy is characterized by myalgia, stiffness, and cramps.
What is the significance of delayed relaxation of deep tendon reflexes in hypothyroidism?
It is a neurological symptom associated with hypothyroidism.
Name the lipid-related symptom seen in hypothyroidism.
Hyperlipidemia - xanthelasma
What is hypercarotenemia, and how is it related to hypothyroidism?
Hypercarotenemia is the presence of high levels of carotene in the blood. It is related to hypothyroidism and is associated with a yellowish discoloration of the skin.
Define myxoedema and list symptoms related to generalised myxoedema in hypothyroidism.
Myxoedema refers to the accumulation of mucopolysaccharide in subcutaneous tissues. Symptoms include doughy skin texture, puffy appearance, myxoedematous heart disease, periorbital edema, pretibial myxoedema, entrapment syndromes, peripheral neuropathy, macroglossia, deep hoarse voice, myxoedema coma.
What symptoms are associated with myxoedematous heart disease?
Dilated cardiomyopathy, bradycardia, dyspnea, pericardial effusion, worsening of heart failure
What is the significance of periorbital edema in hypothyroidism?
Periorbital edema is a symptom of hypothyroidism, distinguishing it from hyperthyroidism.
Name symptoms related to hyperprolactinemia in hypothyroidism.
Menorrhagia, later oligo or amenorrhea
What are the additional symptoms associated with hypothyroidism?
Goiter (in Hashimoto thyroiditis) or atrophic thyroid (in atrophic thyroiditis), impaired cognition, depression, vitiligo, obstructive sleep apnea.
What is the term for the condition in congenital hypothyroidism characterized by dwarfism and limited mental functioning?
Cretinism
What are the thyroid hormone levels in primary hypothyroidism?
TSH is high, and Free T4 and T3 are low.
List some other abnormalities associated with primary hypothyroidism.
- Macrocytosis (↑ MCV)<br></br>2. ↑ Creatinine kinase<br></br>3. ↑ LDL cholesterol<br></br>4. Hyponatremia (due to ↓ renal tubular water loss)<br></br>5. Hyperprolactinemia
Name the thyroid antibodies associated with autoimmune hypothyroidism and their percentages.
- Anti-TPO antibody - 95%<br></br>2. Anti-thyroglobulin - 60%<br></br>3. TSH receptor antibody (blocking) - 10-20%
What are the thyroid hormone levels in secondary hypothyroidism?
TSH is low (or ‘normal’), and Free T4 and T3 are low.
What caution is advised in restoring metabolic rate in hypothyroidism?
Normal metabolic rate should be restored gradually to avoid precipitating cardiac arrhythmias.
How is levothyroxine initiated in younger patients with primary hypothyroidism?
Start levothyroxine at 50-100 µg daily and gradually increase.
What is the recommended initial levothyroxine dosage for elderly patients with a history of ischemic heart disease (IHD) in primary hypothyroidism?
Start levothyroxine at 25-50 µg daily and adjust every 4 weeks according to response.
When should TSH be checked after any dose change in primary hypothyroidism?
TSH should be checked 2 months after any dose change.
How often should TSH be checked once stabilized within the normal range in primary hypothyroidism?
TSH should be checked every 12-18 months once stabilized within the normal range.
How is levothyroxine dose titrated in secondary hypothyroidism?
Titrate the dose of levothyroxine to the total T4 (tT4) level, aiming for the higher end of normal since TSH is unreliable due to low TSH production.
What is myxoedema coma, and who does it typically affect?
Myxoedema coma is a severe, life-threatening condition that typically affects elderly women with long-standing but frequently unrecognized or untreated hypothyroidism.
What is the mortality rate associated with myxoedema coma despite early diagnosis and treatment?
The mortality rate is up to 60% despite early diagnosis and treatment.
Name two investigations conducted in myxoedema coma.
- ECG (Electrocardiogram): Bradycardia, low voltage complexes, varying degrees of heart block, T wave inversion, prolongation of the QT interval.<br></br>2. ABGs (Arterial Blood Gases): Type 2 respiratory failure (hypoxia, hypercarbia, respiratory acidosis).
What is the prevalence of co-existing adrenal failure in myxoedema coma patients?
Co-existing adrenal failure is present in 10% of patients with myxoedema coma.
How is myxoedema coma managed?
Management includes passively rewarming (aim for a slow rise in body temperature), cardiac monitoring for arrhythmias, close monitoring of urine output, fluid balance, central venous pressure, blood sugars, and oxygenation. Broad-spectrum antibiotics are administered, and thyroxine is cautiously given, along with hydrocortisone if adrenal failure is present.