Hypothyroidism occurs at any age but is particularly common among the elderly. It occurs in close to 10% of women and 6% of men > 65. Although typically easy to diagnose in younger adults, it may be subtle and manifest atypically in the elderly.

Hypothyroidism is caused by thyroid hormone deficiency. It is chatacterised by Fatigue, Depression, Modest weight gain, Cold intolerance, Excessive sleepiness, Dry, coarse hair, Constipation, Dry skin, Muscle cramps, Increased cholesterol levels, Decreased concentration, Vague aches and pains, Swelling of the legs.

Primary hypothyroidism:

Primary hypothyroidism is due to disease in the thyroid; thyroid-stimulating hormone (TSH) is increased. The most common cause is probably autoimmune.

The 2nd most common cause is post-therapeutic hypothyroidism, especially after radioactive iodine therapy or surgery for hyperthyroidism or goiter.

Secondary hypothyroidism:

Secondary hypothyroidism occurs when the hypothalamus produces insufficient thyrotropin-releasing hormone (TRH) or the pituitary produces insufficient TSH. Sometimes, deficient TSH secretion due to deficient TRH secretion is termed tertiary hypothyroidism.