These drugs include the typical antipsychotics: phenothiazines such as chlorpromazine (Thorazine), and butyrophenones such as haloperidol (Haldol); atypical antipsychotics such as risperidone (Risperdal) and paliperidone (Invega); gastroprokinetic drugs used to treat gastro-esophageal reflux and medication-induced nausea (such as that from chemotherapy): metoclopramide (Reglan) and domperidone; less often, alpha-methyldopa and reserpine, used to control hypertension; and TRH. The use of estrogen-containing oral contraceptives are also known to increase prolactin levels when taken in high doses >35 μg. The sleep drug ramelteon (Rozerem) also increases the risk of hyperprolactinaemia. Particularly, the dopamine antagonists metoclopramide and domperidone are both powerful prolactin stimulators and have been used to stimulate breast milk secretion for decades. However, since prolactin is antagonized by dopamine and the body depends on the two being in balance, the risk of prolactin stimulation is generally present with all drugs that deplete dopamine, either directly or as a rebound effect. Specific diseases
Prolactinoma or other tumors arising in or near the pituitary — such as those that cause acromegaly may block the flow of dopamine from the brain to the prolactin-secreting cells, likewise, division of the pituitary stalk or hypothalamic disease. Other causes include chronic kidney failure, hypothyroidism, bronchogenic carcinoma and sarcoidosis. Some women with polycystic ovary syndrome may have mildly-elevated prolactin levels.
Dihydropteridine reductase deficiency (DHPRD) is a genetic disorder affecting the tetrahydrobiopterin (BH4) synthesis pathway, inherited in the autosomal recessive pattern. It is one of the six known disorders causing tetrahydrobiopterin deficiency, and occurs in patients with mutations of the QDPR gene. The disease presents with such symptoms as elevated levels of phenylalanine (hyperphenylalaninemia), microcephaly, hypotonus, mental retardation and epileptic seizures. Diagnostics
Besides the traditional analysis of symptoms and investigation of phenylalanine concentrations, patients suspected for DHPRD undergo the assessment of enzymatic activity using the dried blood spot method - this permits to distinguish DHPR deficiency from the other forms of BH4 deficiency. Treatment
Patients are prescribed a phenylalanine-reduced diet, with regular monitoring of phenylalanine levels in the blood. Besides the diet, a patient may be prescribed sapropterin, a synthetic analogue of tetrahydrobiopterin. In order to restore dopamine levels in the central nervous system, patients are given L-dopa in conjunction with an inhibitor of aromatic amino acid decarboxylase that acts outside the nervous system, so as to promote the transformation of L-dopa into dopamine inside the central nervous system, and thus to improve the efficiency of the treatment. Since the insufficient levels of BH4 inhibit the transformation of tryptophan into 5-hydroxytryptophan in a reaction in which BH4 serves as a cofactor of the enzyme tryptophane hydroxylase 2, patients suffer from a lack of serotonin in their CNS. In order to correct this deficiency, they are given 5-hydroxytryptophan. In patients with DHPR deficiency, a pronounced lack of 5-methyltetrahydrofolate (5-MTHF) is observed in the central nervous system.