Which condition is indicated by a woman who has weight gain, lethargy, and a pulse rate of 55 beats/minute?

Hypothyroidism is a condition characterized by an underactive thyroid gland, leading to insufficient production of thyroid hormones. This hormonal deficiency can result in a number of symptoms, including weight gain, fatigue, and bradycardia, which refers to a slower-than-normal heart rate, typically indicated by a pulse rate below 60 beats per minute.

In this case, the woman's weight gain suggests an impaired metabolic rate, which is common in hypothyroidism due to the reduced levels of thyroid hormones that are essential for regulating metabolism. Lethargy is also a hallmark symptom, as thyroid hormones play a crucial role in energy levels and overall vitality. Additionally, the low pulse rate of 55 beats per minute aligns with the bradycardia often seen in individuals with hypothyroidism, as the decreased metabolic activity can lead to a slower heart rate.

Thus, the combination of weight gain, lethargy, and bradycardia strongly points towards hypothyroidism as the underlying cause of these symptoms. The other conditions referenced do not typically present with this specific combination of signs. For instance, hyperthyroidism would generally lead to weight loss and increased heart rate, while Cushing's syndrome and Addison's disease have different symptom profiles altogether.