Prolactinoma is readily detected in menstruating women because of galactorrhea and irregular menses, but in men, this tumor can be difficult to recognize. Symptoms and signs of hypogonadism (see Table 1) may not become obvious, unless the tumor becomes large, or hyperprolactinemia and gonadotropin deficiency become severe. Therefore, in men, the diagnosis of prolactinoma is often delayed until a visual field defect or other symptoms secondary to tumor pressure on surrounding structures occur (e.g., headaches, seizures, altered personality, cranial nerve palsies, symptoms related to the deficiencies of other pituitary hormones, and hydrocephalus). With long-standing hypogonadism, the testes are usually soft but of normal size and the semen analysis frequently reveals low semen volume, oligospermia, or azoospermia (14-16). Most men with hyperprolactinemia have low-normal serum levels of LH, testosterone, and DHT, and low-frequency and low-amplitude spontaneous LH secretory episodes (17), together with a normal increase in serum LH levels after GnRH administration (10). The identification of high PRL levels is the beginning of the diagnostic process; however, hyperprolactinemia should be correctly identified and other causes should be excluded. PRL levels in patients with PRL-secreting adenomas are usually higher than 100 ng/ml and are proportional to the size of the tumor. Lower values may be associated with drugs, pituitary stalk compression, renal failure, cirrhosis, hypothyroidism, and polycystic ovary disease (14). Macroprolactinemia is a molecular weight variant increasing the serum PRL levels because of reduced hormone clearance; it is usually unassociated with clinical problems. Computed tomography (CT) and magnetic resonance imaging (MRI) allow for detailed noninvasive imaging of the pituitary gland. Both methods are effective in identifying large pituitary tumours; CT is better for defining bone erosions and calcified structures, but MRI with gadolinium enhancement provides superior anatomical detail to detect prolactinomas and their relationship to neighboring structures. MRI is more efficacious than CT to identify microadenoma (18-20).
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