Hypothyroidism

Question 1

How common is it?

Answer 1

• Common - 4/1000/yr.

Question 2

What causes it?

Answer 2

Primary autoimmune hypoT

• Primary atrophic hypoT - 6:1 F:M - Common. Diffuse lymphocyte infiltration of thyroid, leading to atrophy, hence no goitre.
• Hashimoto’s thyroiditis - Goitre due to lymphocytic and plasma cell infiltration. Commoner in woman aged 60-70.

Other causes of primary hypoT

• Iodine deficiency
• Post thyroidectomy or radioiodine treatment
• Drug induced - antithyroid drugs, amiodarone, lithium, iodine.
• Subacute thyroiditis - temporary hypoT after hyperT phase.

Secondary hypoT
- Not enough TSH (hypopituitarism) - v.rare.

Question 3

Risk factors?

Answer 3

• Autoimmune seen with other AI disorders (T1 DM, addison’s, PA). Turner’s, Down’s, CF, primary billiary cirrhosis, ovarian hyperstimulation. POEMS syndrome = polyneuropathy, organomegaly, endocrinopathy, m-protein band.
• Genetic - Dyshormonogenesis: genetic (autosomal recessive) = defect in hormone synthesis.

Question 4

How does it present?

Answer 4

Symptoms
- Tired, sleepy, lethargic, low mood, cold-disliking, weight gain, constipation, menorrhagia, hoarse voice, reduced memory/cognition, dementia, myalgia, cramps, weakness.

Signs - BRADYCARDIC Bradycardia, reflexes relax slowly, ataxia (cerebellar), dry thin hair/skin, yawning/drowsy/coma, cold hands, ascites, round puffy face/double chin/obese, defeated demeanour, immobile + ileus, CCF.

Question 5

Other conditions that may present similarly?

Answer 5

Depression, Alzheimer’s, anaemia…

Question 6

Investigations?

Answer 6

• TFTs - ↑TSH; T4↓ (in rare secondary hypothyroidism: ↓T4 and ↓TSH due to lack from the pituitary.
• ↑Triglyceride and cholesterol; macrocytosis.

Question 7

Treatments?

Answer 7

• Healthy and young – Levothyroxine (T4). Once normal check TSH yearly.
• Elderly + ischaemic heart disease – increase dose slowly.
• Amiodarone – 2% get thyroid problems. Hypothyroidism can be caused by iodine excess (T4 release inhibited).