Hypothyroidism

Question 1

What are the causes of hypothyroidism?

Answer 1

(Congenital)
(Acquired) Primary hypothyroidism: insufficient thyroid hormone production e.g. Hashimoto thyroiditis, Postpartum thyroiditis, De Quervain thyroiditis
Secondary hypothyroidism: pituitary disorders (e.g., pituitary adenoma) → TSH deficiency
Tertiary hypothyroidism: hypothalamic disorders → thyrotropin-releasing hormone (TRH) deficiency

Question 2

What are the effects of hypothyroidism?

Answer 2

(General) decrease in the basal metabolic rate → apathy, slowed cognition; skin dryness, alopecia; ↑ low-density lipoproteins, ↑ triglycerides
(Decreased sympathetic activity) Decreased sweating
Constipation
Bradycardia
(Hyperprolactinemia) prolactin production is stimulated by TRH

Question 3

What are the clinical features of hypothyroidism?

Answer 3

(General) Fatigue, bradykinesia
Cold intolerance
Hair loss and cold, dry skin
Weight gain (despite poor appetite)
Constipation
Bradycardia
(Skin)Dry (anhydrosis), cold, yellowish skin
Non-pitting oedema (e.g. hands, face)
Dry, coarse scalp hair, loss of lateral aspect of eyebrows
(Neurological)Decreased deep tendon reflexes
Carpal tunnel syndrome

Question 4

How is hypothyroidism diagnosed?

Answer 4

(Congenital) Neonatal screening to measure TSH levels 24–48 hours after birth
(Acquired) TSH levels + Free T4 levels

Question 5

What is the treatment for hypothyroidism?

Answer 5

(Healthy/Young) Levothyroxine (T4)

Lower doses for elderly or with ischaemic heart disease