What condition is treated with hormone replacement therapy to relieve symptoms of estrogen deficiency?

Hormone replacement therapy (HRT) is primarily used to treat symptoms caused by estrogen deficiency, particularly during menopause. Menopause is a natural biological process that occurs in women, typically in their late 40s to early 50s, where the ovaries reduce hormone production, resulting in lower estrogen levels. This decline can lead to various symptoms such as hot flashes, night sweats, mood changes, and vaginal dryness, making hormone replacement an effective treatment to alleviate these discomforts and improve quality of life.

In contrast, the other conditions listed do not specifically relate to estrogen deficiency. Hyperthyroidism is a condition related to excessive thyroid hormone production, osteoporosis is characterized by weakened bones and is associated with various factors, including aging and nutritional deficiencies rather than solely estrogen deficiency, and thyroid cancer involves malignant growths in the thyroid gland that may not be influenced by estrogen levels. Therefore, menopause is the condition most directly treated with hormone replacement therapy to counteract the effects of decreased estrogen.