Lesion in hypothalamus leads to hyperprolactinemia.

Lesions of specific areas of the hypothalamus leads to specific defects in pituitary hormone secretion. For example, Prolactin (PRL) is an anterior pituitary hormone which is secreted in a pulsatile manner. Unlike other tropic hormones secreted by the anterior pituitary gland, PRL secretion is controlled primarily by inhibition from the hypothalamus and it is not subject to negative feedback directly or indirectly by peripheral hormones. This explains that a mass lesion in the hypothalamic or pituitary stalk area, results in a decrease of anterior pituitary hormones whereas it causes the elevation in PRL concentrations . Thyrotropin-releasing-hormone (TRH) is the main PRL-releasing factor and thus hyperprolactinemia is found in primary hypothyroidism. Other factors, like GHRH can also stimulate PRL release. Thus, the possible mechanism of elevated PRL levels is pituitary stalk compression by a tumor, leading to a decrease of PRL inhibition by dopamine from the hypothalamus and resulting into hyperprolactinemia.