SAT-033 Hyperprolactinemia in a Patient with Tyrosine Hydroxylase Deficiency: A Rare Disease

Abstract Disclosure: S.D. Simanchalam: None. S. Rajoo: None. N.H. Mohd Makhatar: None. Y.H. Chin: None. Tyrosine Hydroxylase (TH) deficiency is a rare, autosomal recessive disorder that impairs dopamine biosynthesis, which leads to neurological and endocrine abnormalities. Neurologically, it manifests symptoms like hypotonia, dystonia, and autonomic dysfunction, while endocrine complications such as hyperprolactinemia. A 19-year-old girl was diagnosed with TH deficiency at 14 months following bilateral dystonia, hypotonia, and abnormal eye movements. The cerebrospinal fluid (CSF) neurotransmitter analysis revealed markedly low levels of homovanillic acid (HVA) at 40 nmol/L (reference: 295-932 nmol/L), which indicates dopamine deficiency and, along with that, slightly reduced 5-hydroxyindoleacetic acid (5-HIAA) level. A mutation test on the TH gene confirmed the diagnosis of tyrosine hydroxylase deficiency. She was treated with Sinemet (levodopa-carbidopa) to manage the motor symptoms. At the age of 15 years, she attained menarche but developed secondary amenorrhea by the age of 16, accompanied by progressive hyperprolactinemia 4503 mIU/L (reference 102.0 – 496.0 mIU/L). MRI pituitary ruled out structural causes, and there were no adenomas. The transabdominal ultrasound revealed a small uterus and follicular cysts, consistent with suppressed hypothalamic-pituitary-gonadal (HPG) axis function. Sinemet was insufficient to suppress prolactin, as it does not replace hypothalamic dopamine, which usually inhibits prolactin secretion. Cabergoline, a dopamine D2 receptor agonist, was initiated and significantly reduced the prolactin to 187 mIU/L (reference 102.0 – 496.0 mIU/L) within a month of treatment. It also alleviates the endocrine dysfunction, during which the menstrual cycles resume subsequently. This case highlights the interplay between dopamine deficiency and hyperprolactinemia in TH deficiency, emphasizing the need for cabergoline therapy to restore hormonal balance and prevent complications such as amenorrhea, ovarian dysfunction, and osteoporosis. A multidisciplinary approach is essential for long-term management and optimal outcomes. Presentation: Saturday, July 12, 2025