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9092909 
Journal Article 
Primary Hypothyroidism with Exceptionally High Prolactin-A Really Big Deal 
Khorassanizadeh, R; Sundaresh, V; Levine, SN; , 
2016 
1 
World Neurosurgery
ISSN: 1878-8750
EISSN: 1878-8769 
ELSEVIER SCIENCE INC 
NEW YORK 
675.e11-675.e14 
English 
27155380 
WOS:000380365000133 
Primary hypothyroidism can cause both hyperprolactinemia and pituitary hyperplasia. The degree of hyperprolactinemia is generally modest, and rarely do prolactin concentrations exceed 100 ng/mL (4.34 nmol/L). This combination of hyperprolactinemia and pituitary gland enlargement might raise suspicion for a prolactinoma or a nonfunctioning adenoma limiting the ability of hypothalamic dopamine to inhibit prolactin production, the so-called "stalk effect."We describe a 30-year-old female with headaches, galactorrhea, and hyperprolactinemia with a presumptive diagnosis of a prolactinoma. She had hypothyroidism after treatment of Graves disease at age 17 years but was noncompliant with levothyroxine replacement. Thyroid-stimulating hormone (TSH) was 263 mIU/L, FT4 was 3.01 pmol/L, and prolactin was 323 ng/mL (14.06 nmol/L). Magnetic resonance imaging (MRI) demonstrated increased volume of the pituitary gland with homogeneous enhancement with gadolinium. Levothyroxine treatment for 2 weeks decreased her TSH to130 mIU/L, but her total prolactin remained elevated at 386 ng/mL (16.78 nmol/L). Further testing identified that 76% of the total prolactin was macroprolactin.Primary hypothyroidism can cause hyperprolactinemia, and prolonged disease may lead to pituitary hyperplasia. However, a marked elevation of prolactin should raise suspicion to investigate additional etiologies for hyperprolactinemia. Our case exemplifies a dual etiology for hyperprolactinemia and pituitary hyperplasia caused by both hypothyroidism and macroprolactin. This knowledge is invaluable for clinicians to avoid unnecessary management with dopamine agonists and/or surgery. This patient's prolactin was 323 ng/mL (14.06 nmol/L). Before our case, the highest prolactin in a hypothyroid patient reported in the literature was 253 ng/mL (11.0 nmol/L).