Journal of Psychiatric Practice Vol. 18, No. 2 126 March 2012 Hyperprolactinemia is a common consequence of treatment with an antipsychotic medication. It can result in hypogonadism due to the inhibitory effect of elevated prolactin levels on the hypothalamic-pituitary-gonadal hormonal axis. We present a case of hypogonadism sec- ondary to hyperprolactinemia in a patient tak- ing antipsychotic medication, with radiological evidence of a pituitary microadenoma. The rel- evance and investigation of hyperprolactinemia in patients being treated with antipsychotic medications are discussed. (Journal of Psychiatric Practice 2012;18:126–129) KEY WORDS: prolactin, hyperprolactinemia, anti- psychotics, pituitary adenoma CASE PRESENTATION A 35-year-old female inpatient with a diagnosis of para- noid schizophrenia was referred to the endocrine department for management of chronic hyperpro- lactinemia. In the previous 7 years, she had been treat- ed with risperidone, olanzapine, haloperidol, clozapine, amisulpride, quetiapine, and flupenthixol. During this period, her prolactin levels ranged from 1,203–3,193 mIU/L (normal range = 102–496 mIU/L).* At the time of referral, her mental state was stable on a combina- tion of amisulpride 400 mg/day and aripiprazole 20 mg/day. She was not taking oral contraceptive medica- tion and was on no other medication. She complained of galactorrhea, decreased libido, oligomenorrhea, back pain, and hair thinning. On examination, the patient had no visual field defect, acne, goitre, or hirsutism. No clinical features of Cushing’s syndrome or acromegaly were present. Hormone levels were prolactin: 2,410 mIU/L (normal 102–496 mIU/L) (113.7 μg/L, normal 4.8–23.4 μg/L), thyroid stimulating hormone: 1.24 mIU/L (normal 0.27–4.2 mIU/L), free thryoxine: 14.2 pmol/L (normal 12–22 pmol/L), follicle stimulating hormone: 6.7 IU/L (normal 3.5–12.5 IU/L follicular phase), luteinizing hormone: 3.7 IU/L (normal 2.4–12.6 IU/L follicular phase), estradiol: 111 pmol/L (normal 46–607 pmol/L follicular phase), testosterone: 1.7 nmol/L (normal 0.2–2.9 nmol/L), and sex hormone binding globulin: 60 nmol/L (normal 40–80 nmol/L). Renal function was normal. A pituitary magnetic resonance imaging (MRI) scan showed a new 2.5 mm microadenoma which had not been present on a previous MRI study 7 years earlier. There was no radiological evidence of stalk compression. Discussion and Management Objectives Prolactin is produced and secreted by lactotrophs of the anterior pituitary gland. Hypothalamic dopamine acts on the lactotroph cells to inhibit prolactin release, while thyrotropin releasing hormone (TRH), nipple stimula- tion, and chest wall injury stimulate prolactin secre- tion. 1 Induction of lactation in the postpartum period is the only functional role of prolactin described in healthy humans; the hormone does not appear to be involved in breast development. Prolactin levels remain relatively stable during the day and can thus be measured at any time. 2 Due to slight normal fluctuations, repeat testing is advised to confirm hyperprolactinemia. The presence of significant concentrations of macroprolactin (pro- lactin bound to IgG rendering it detectable to the pro- lactin assay but biologically inert) is common and should be excluded. 3 The phenomenon of stress-induced (e.g., venepuncture) hyperprolactinemia is well docu- mented and clinicians should be wary of misinterpret- ing mildly elevated prolactin levels. Moderate to severe hyperprolactinemia produces hypogonadism, predomi- CARROLL: Wellington Regional Hospital, Capital and Coast DHB, New Zealand; CHRISTODOULOU and BAYNES: Ealing Hospital NHS Trust, Southall, UK; KAHN: Columbia University College of Physicians and Surgeons. DOI: 10.1097/01.pra.0000413279.95843.b5 *Prolactin concentrations expressed in mIU/L can be convert- ed to μg/L by dividing by 21.2: patient’s range = 56.7–150.6 μg/L (normal range = 4.8–23.4 μg/L). Hyperprolactinemia in a Patient with a Pituitary Adenoma Receiving Antipsychotic Drug Therapy Clinical Case Discussion Case presentation: RICHARD W. CARROLL, MB ChB POLYXENI CHRISTODOULOU, MB ChB KEVIN C. R. BAYNES, MB BS, PhD Case discussion: DAVID A. KAHN, MD Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.