Hypothyroidism: This condition can lead to both weight loss (starving appearance) due to increased metabolism in some cases, and galactorrhea due to the elevated TRH (thyrotropin-releasing hormone) levels stimulating prolactin release. The link between hypothyroidism and galactorrhea, although less common, makes it a plausible single most likely diagnosis given the combination of symptoms.

Prolactinoma: A type of pituitary tumor that secretes prolactin, leading to galactorrhea. Weight loss or a starving appearance could be secondary to the tumor's effects on appetite regulation or due to associated hormonal imbalances affecting metabolism.
Hyperthyroidism: Although less directly linked to galactorrhea, hyperthyroidism can cause significant weight loss (leading to a starving appearance) and, in rare cases, can affect prolactin levels indirectly.

Pituitary Apoplexy: A medical emergency where a pituitary tumor suddenly hemorrhages or infarcts, potentially leading to acute hormonal deficiencies or excesses, including prolactin. The sudden onset of symptoms, including severe headache, visual disturbances, and acute endocrine dysfunction, makes this a critical diagnosis not to miss.
Cranial Lesions (e.g., Craniopharyngioma): Tumors or lesions in the sellar/suprasellar region can compress or invade the pituitary gland and hypothalamus, leading to a variety of endocrine abnormalities, including galactorrhea and changes in appetite or metabolism.

Acromegaly: Caused by excess growth hormone, usually due to a pituitary adenoma. While it primarily causes growth of hands, feet, and facial features, it can also lead to changes in body composition and, very rarely, galactorrhea if there's a co-secretion of prolactin.
Tuberous Sclerosis Complex (TSC): A genetic disorder that can cause a variety of tumors, including pituitary tumors that might secrete prolactin, leading to galactorrhea. Weight loss could be due to other systemic effects of the disease.