Hormones, Impotence, and the Temporal Lobe
// October 29th, 2010 // No Comments » // Hormones, Impotence
Our understanding of the hormonal interplay necessary for normal male sexual function continues to evolve. Medical professionals used to consider the pituitary the master gland, the agent that doled out specific instructions to regulate the function of the other endocrine glands — thyroid, adrenals, and testicles. Twenty years ago, it became clear that the pituitary could not discharge this important regulatory function on its own but was beholden to a higher hormonal power located in the hypothalamus. The pituitary was then more properly recognized as an intermediary existing to fulfill the hormone directives issued by the hypothalamus.
Just as we became comfortable with this concept, another area of the brain, the temporal lobe, entered the playing field. The role of the temporal lobe in hormone secretion appears to be more meddlesome than regulatory. This is especially true when viewing the effect of temporal lobe influences on male sexual function.
Scientists studying the temporal lobe in humans were fully aware of its critical role in the reproductive and sexual function of animals. Experimental destruction of a specific portion of the temporal lobe (the amygdala) caused testicular degeneration in male rats and cats. Implants of estrogen in rabbits’ amygdalae provoked hyperprolactinemia. But how do these animal experiments relate to humans?
As mentioned, some men suffer from a temporal lobe disorder called temporal lobe epilepsy (TLE). They have decreased libido and are often impotent. Some of these men have low serum testosterone levels; others have increased blood levels of prolactin.
TLE is different from other forms of epilepsy. Early symptoms are subtle and are characterized by a series of “spells.” Sudden attacks of abdominal pain, dizziness, fugue states, bed-wetting, and rage as well as auditory hallucinations may be clues to the presence of a temporal lobe disorder. The coexistence of a form of epilepsy and a hormone disorder initially created a dilemma for the physician. Which condition should be treated first?
Experience provided the answer. Patients with TLE and hypogonadism are, at first, unresponsive to testosterone injections, and those with TLE and hyperprolactinema do not benefit from bromocriptine. (This distinguishes them from other hypogonadal or hyperprolactinemic men.) Antiseizure medications such as phenytoin (Dilantin) or carbarnazepine (Tegretol) must be the first line of treatment. Then conventional hormone therapy is beneficial. (Frequently, the antiseizure medications not only control TLE symptoms but also allow serum hormone levels to return to normal.)
The diagnosis of TLE requires specialized testing. An unusual type of brain-wave test, the sleep-deprived electroencephalogram (EEG), detects subtle disturbances in temporal lobe electrical activity. A new diagnostic probe, single photon emission computerized tomography (SPECT scan), may also help. The SPECT scan registers different colors in relation to blood flow. Areas of greatest blood flow in the brain show up with the whitest colors. Since increased blood flow is one characteristic of seizureprone brain tissue, these areas light up on SPECT scan.
Hormone disorders are perhaps the most easily diagnosed causes of impotence, and hormone measurements should be an integral part of the early evaluation of the impotent man. Hormone abnormalities, once detected, can be treated with some dispatch and considerable success.
