What is the most likely diagnosis for a woman exhibiting weight gain, irregular periods, and dry skin?

The symptoms of weight gain, irregular periods, and dry skin strongly suggest hypothyroidism. In this condition, the thyroid gland does not produce sufficient thyroid hormones, which play a key role in regulating metabolism and various body functions.

Weight gain occurs due to the slowing of metabolic processes, as the body is unable to effectively use energy. Irregular periods can happen because hypothyroidism can affect the hormonal balance necessary for regular menstrual cycles. Additionally, dry skin is a common symptom, as slowed metabolism can lead to reduced moisture in the skin due to decreased sweat and oil production.

In summary, the combination of weight gain, menstrual irregularities, and dry skin aligns well with hypothyroidism, making it the most likely diagnosis for this patient.