Hypothyroidism: The patient's TSH level is slightly elevated (2.56) and free T4 is at the lower end of the normal range (0.7), which may indicate subclinical hypothyroidism. This condition can cause weight gain and difficulty losing weight despite a healthy diet and exercise.

Insulin Resistance/Pre-diabetes: The patient's difficulty losing weight despite a healthy lifestyle may indicate insulin resistance, which can lead to weight gain and metabolic problems.
Polycystic Ovary Syndrome (PCOS): PCOS is a common endocrine disorder that can cause weight gain, insulin resistance, and hormonal imbalances, making it difficult to lose weight.
Cushing's Syndrome: Although less common, Cushing's syndrome can cause weight gain, particularly in the abdominal area, and can be difficult to diagnose.

Pituitary Adenoma: A pituitary adenoma can cause hypopituitarism, leading to hormonal imbalances, including thyroid hormone deficiency, which can cause weight gain and difficulty losing weight.
Adrenal Insufficiency: Adrenal insufficiency can cause weight gain, fatigue, and metabolic problems, and can be life-threatening if left untreated.
Thyroid Cancer: Although rare, thyroid cancer can cause weight gain and difficulty losing weight, and can be diagnosed with a thorough thyroid evaluation.

Leptin Deficiency: A rare genetic disorder that can cause severe obesity and difficulty losing weight.
Pseudohypoparathyroidism: A rare genetic disorder that can cause weight gain, short stature, and other metabolic problems.
Growth Hormone Deficiency: A rare condition that can cause weight gain, fatigue, and metabolic problems, particularly in adults.