A 39-year-old woman presents with visual disturbances due to a pituitary tumor. What is the most common clinical effect of such tumors?

In cases of pituitary tumors, the most common clinical effect is hyperprolactinemia. Pituitary adenomas, particularly prolactinomas, are often characterized by excessive secretion of prolactin, which is a hormone produced by the lactotroph cells in the pituitary gland. This excess prolactin can lead to various symptoms, such as galactorrhea (production of breast milk in individuals who are not pregnant or nursing) and menstrual irregularities in women, including amenorrhea.

While vision loss is a significant concern due to the tumor's location and potential pressure on the optic chiasm, hyperprolactinemia is more directly linked to the hormonal dysregulation caused by the growth of the tumor itself. Similarly, hypopituitarism (reduced secretion of one or more pituitary hormones) may occur in more advanced cases or larger tumors but is not typically the most common presenting feature in the early stages of a prolactinoma. Increased libido is generally not associated with prolactin-producing tumors, as elevated prolactin levels can suppress gonadal function, which may lead to reduced libido. Thus, considering the hormonal dynamics involved, hyperprolactinemia stands out as the most common and