**5. Prolactinoma**

Prolactinoma is the most common type in secretary pituitary adenoma with an incidence of 50% of all pituitary adenomas. It is typically commonly seen in women aged 20–50 years old. As stated previously, prolactin is under continuous inhibition from dopamine, a PIF, secreted from hypothalamus through the pituitary stalk. Stalk dysfunction, either by compression or hypothalamic lesion, will result in loss of prolactin inhibition with subsequent prolactin elevation. Prolactinomas arise from monoclonal expansion of pituitary lactotrophs, however, 5–10% of prolactinomas can co-secrete GH resulting in superimposed gigantism/ acromegaly [10]. As the disruption of hormone homeostasis causes subtle symptoms in some prolactinoma patients, it is the most likely tumor to become large enough to cause clinical manifestations of mass effect compared to other secreting tumors.

#### **5.1 Signs and symptoms**

Hyperprolactinemia symptoms in males include decreased libido, sexual dysfunction and oligozoospermia (due to secondary hypogonadism). In perimenopause females, amenorrhea-galactorrhea syndrome is usually seen, which is a triad of galactorrhea, amenorrhea and infertility. In children and adolescents, growth arrest, pubertal delay and primary amenorrhea are frequently seen. Symptoms may also be due to mass effect which may cause headache, vision field deficits, cranial nerve palsy, seizure, and hydrocephalus.


#### **Table 3.**

*Differential diagnosis of hyperprolactinemia.*
