Objective: We aimed to investigate the mechanisms of hypogonadism which develops after head injury.
Design: Pulsatile secretion of LH was studied in subjects 6-10 days after major head injury.
Patients: We studied five male subjects admitted with major head injuries and six healthy age-matched control subjects.
Measurements: During the pulsatility study, LH was measured at 5-minute intervals for 4 hours and 15-minute intervals for a further 2 hours. In addition, testosterone and LH were measured on Days 1-5, 14 and after 3-6 months.
Results: The analysis of pulsatile secretion of LH demonstrated an LH pulse frequency similar to control subjects, but a significantly reduced LH pulse amplitude (P less than 0.001, fixed threshold method; P less than 0.02, Detect method). Both testosterone and LH levels were reduced after injury with the nadir occurring on Day 4.
Conclusions: Hypogonadism after head injury is due to defective LH secretion, with normal pulse frequency but a reduced pulse amplitude.