PRL and familial hyperprolactinemia: Among of these patients with HPRL, in 87 (26.7%) there was an identifiable condition that could account for the increased PRL levels (secondary HPRL): 61 patients were attributable to overt or subclinical hypothyroidism, evaluated on the basis of normalization of TSH and PRL concentrations with L-thyroxine, except in six patients who had MPRL and remained hyperprolactinemic despite the normalization of TSH levels; 22 patients were attributable to prolactinomas, and 4 patients were attributable to the use of medications.