What is the primary diagnosis for a patient presenting with significant skin dryness and weight gain?

The primary diagnosis for a patient exhibiting significant skin dryness and weight gain is hypthyroidism. This condition occurs when the thyroid gland is underactive and does not produce enough thyroid hormones, which play a crucial role in regulating metabolism, energy levels, and overall skin health.

In hypothyroidism, the slowed metabolism can lead to weight gain, while skin dryness can result from decreased oil production and changes in skin hydration and texture. These symptoms are commonly associated with the condition due to the impact of thyroid hormones on various bodily functions, including metabolism and skin health.

Cushing's syndrome and adrenal insufficiency could also lead to weight changes, but they are associated with different symptoms and mechanisms. Cushing's syndrome typically presents with other features such as a rounded face and purple abdominal striae, while adrenal insufficiency can cause low energy and hypotension, but doesn't primarily involve dryness as a prominent symptom. Hyperthyroidism would present the opposite metabolic symptoms, such as weight loss and excessive sweating. Hence, hypthyroidism aligns most closely with both significant skin dryness and weight gain.