Gonadotropin levels were measured in 65 postmenopausal women admitted to the intensive care unit. Sixteen patients (25%) were hypogonadotropic as measured by luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels of 5 IU/L or less, and only 20 patients (31%) were found to have gonadotropin levels within the expected postmenopausal range (greater than or equal to 30 IU/L). No significant differences in prolactin or free thyroxine levels were found, but the cortisol level was higher and the total thyroxine level lower in the hypogonadotropic group. The patients in the hypogonadotropic group also seemed more seriously ill, with a longer duration of hospitalization, an increased total number of days in the intensive care unit, an increased number of days in the intensive care unit before gonadotropin sampling, a higher incidence of parenteral hyperalimentation, lower serum albumin levels, and higher mortality. Stimulation of the gonadotropin-releasing hormone performed on 10 patients showed a blunted response in patients with baseline LH and FSH levels of 10 IU/L or less. Of 10 patients followed up sequentially, 6 showed a rise in gonadotropin levels that paralleled recovery, 1 died with low gonadotropin levels, and 3 continued to have low gonadotropin levels 17, 34, and 82 days, respectively, after initial screening. Critically ill postmenopausal women may exhibit a marked fall in gonadotropin, LH, and FSH levels. This disease in gonadotropin levels in response to illness is reversible and results from pituitary unresponsiveness to gonadorelin hydrochloride.