- To assess nonarticular tenderness and prevalence of fibromyalgia syndrome (FMS) in hyperprolactinemic subjects. Twenty-one consecutive women with hyperprolactinemia (HPRL) and 44 consecutive women with normal prolactin levels (PRL) were examined in the fertility unit by one observer during a 24-month period. Mean age was 31 years, range 22-46 years. Hyperprolactinemia was defined as PRL levels > 24.5 ng/ml (immunoradiometric assay). In all women, a count of 18 tender points (TP) was conducted by thumb palpation. Tenderness of some of the TP sites (9 points) as well as control point sites (4 points) was further assessed using a Chatillon dolorimeter. All women were questioned about the presence of widespread pain or aching. Women were considered to have FMS if they met the American College of Rheumatology (ACR) criteria for diagnosis. Of the 21 women with HPRL, 15 (71%) had FMS vs only 2 of 44 (4.5%) normoprolactinemic women (p < 0.0001). Thresholds of tenderness of 9 fibrositic points were 2.7 (1.5) kg [mean (standard deviation)] for HPRL women vs 5.0 (1.4) (kg) for women with normal PRL (p < 0.0001). Thresholds of tenderness of 4 control points were 5.2 (1.5) (kg) for women with HPRL vs 6.8 (1.1) (kg) for normoprolactinemic women (p < 0.0001). The frequency of FMS was directly associated with the level of PRL. We suggest that FMS is very common in a subset of women with HPRL and that its frequency is directly associated with the degree of hyperprolactinemia. Women with HPRL have lower thresholds of tenderness than women with normal PRL. More studies are needed to clarify the relationships between PRL, FMS and tenderness.