Plasma prolactin increase following electric stimulation of the amygdala in humans

Clinical utility of serum prolactin and lactate concentrations to differentiate epileptic seizures from non-epileptic attacks in the emergency room

PURPOSE

To evaluate the diagnostic utility of serum prolactin (PRL) and lactate (LAC) concentrations for patients presenting with either or both convulsions and transient loss of consciousness (TLOC) in the emergency room (ER).

METHODS

This was a retrospective single-center study conducted in a tertiary care hospital ER. Medical records of consecutive patients who presented with convulsions or TLOC between January 2018 and December 2020 were reviewed. Patients with an ER diagnosis of epileptic seizures, psychogenic non-epileptic seizure (PNES), and syncope were selected for analysis. Serum PRL and LAC concentrations were measured within 3 h of the event and compared between groups.

RESULTS

Among the 440 eligible patients, 173 (39.3%) were included for analysis. Serum PRL concentration was significantly higher in patients with epileptic seizures with convulsions than in those with PNES with convulsions (p < 0.001) and convulsive syncope (p = 0.023). Serum LAC concentration was not significantly elevated in patients with convulsive syncope. Using a PRL cut-off value of 24.0 ng/mL, serum PRL concentration had 100.0% sensitivity and 82.9% specificity for differentiating between PNES and other attacks without convulsions.

CONCLUSION

Elevated serum PRL with normal serum LAC concentration in patients who have attacks with convulsions suggests convulsive syncope. Serum PRL concentration is useful in the diagnosis of PNES with convulsions. However, serum LAC concentration is not useful as a routine screening test for attacks without convulsions in the ER.

Seizure duration may increase thyroid-stimulating hormone levels in children experiencing a seizure

Objective

Variations in hormone levels are a direct effect of epileptic discharges in both animals and humans, and seizure can affect the hypothalamus–pituitary–thyroid axis. The purpose of this study was to determine which parameters could affect the alternation of thyroid hormones in children experiencing seizure.

Methods

We retrospectively reviewed the medical records of 181 pediatric patients with seizure and compared three thyroid hormones (serum thyroid-stimulating hormone [TSH], free thyroxine [fT4], and triiodothyronine [T3]) between initial (admission to hospital) and follow-up (2 weeks later) testing.

Results

Multivariable logistic regression models were used to determine which six parameters (gender, age, seizure accompanying with fever, seizure type, seizure duration, and anti-epileptic drug medication) could help to explain the higher initial TSH levels in pediatric seizure. Only seizure duration in patients with an increase in TSH levels was significantly longer compared with patients with normal TSH at the time of initial testing.

Conclusion

Neuronal excitability by seizure can cause thyroid hormonal changes, which likely reflects changes in hypothalamic function.

Biomarkers in the diagnosis and study of psychogenic nonepileptic seizures: A systematic review

OBJECTIVE

Video electroencephalography (vEEG) is the gold-standard method for diagnosing psychogenic nonepileptic seizures (PNES), but such assessment is expensive, unavailable in many centers, requires prolonged hospitalization, and many times is unable to capture an actual seizure episode. This paper systematically reviews other non-vEEG candidate biomarkers that may facilitate both diagnosis and study of PNES as differentiated from epileptic seizures (ES).

METHODS

PubMed database was searched to identify articles between 1980 and 2015 (inclusion: adult PNES population with or without controls, English language; exclusion: review articles, meta-analyses, single case reports).

RESULTS

A total of 49 studies were examined, including neuroimaging, autonomic nervous system, prolactin, other (non-prolactin) hormonal, enzyme, and miscellaneous marker studies. Functional MRI studies have shown PNES is hyperlinked with dissociation and emotional dysregulation centers in the brain, although conflicting findings are seen across studies and none used psychiatric comparators. Heart rate variability suggests increased vagal tone in PNES when compared to ES. Prolactin is elevated in ES but not PNES, although shows low diagnostic sensitivity. Postictal cortisol and creatine kinase are nonspecific. Other miscellaneous biomarkers (neuron specific enolase, brain derived neurotropic factor, ghrelin, leptin, leukocytosis) showed no conclusive evidence of utility. Many studies are limited by lack of psychiatric comparators, size, and other methodological issues.

CONCLUSION

No single biomarker successfully differentiates PNES from ES; in fact, PNES is only diagnosed via the negation of ES. Clinical assessment and rigorous investigation of psychosocial variables specific to PNES remain critical, and subtyping of PNES is warranted. Future investigational and clinical imperatives are discussed.

Thyroid-stimulating hormone elevation misdiagnosed as subclinical hypothyroidism following non-convulsive status epilepticus: a case report

Introduction

Non-convulsive status epilepticus is a form of epileptic seizure that occurs without convulsions. Recent reviews suggest that the diagnosis of non-convulsive status epilepticus remains difficult. Here, we report the case of a patient with thyroid-stimulating hormone elevation misdiagnosed as subclinical hypothyroidism following non-convulsive status epilepticus.

Case presentation

Our patient was a 68-year-old Japanese woman. The results of endocrine testing after her first episode of non-convulsive status epilepticus suggested latent subclinical hypothyroidism: she had elevated thyroid-stimulating hormone with normal levels of free tri-iodothyronine and free thyroxine. On examination, a diagnosis of thyroid disorder was not supported by other test results and our patient remained untreated. A follow-up examination revealed that her thyroid-stimulating hormone levels had spontaneously normalized. When she consulted another doctor for confusion, the transient increase in thyroid-stimulating hormone levels following non-convulsive status epilepticus was mistaken for subclinical hypothyroidism, and unfortunately treated with levothyroxine. Our patient then experienced levothyroxine-induced non-convulsive status epilepticus.

Conclusions

In this report, we suggested possible mechanisms for latent hypothyroid-like hormone abnormality following epileptic seizures and the possibility of provoking epileptic seizures by administering levothyroxine for misdiagnosed subclinical hypothyroidism.

Hormonal alterations following seizures

Postictal increases in prolactin (PRL), luteinizing hormone, and follicle-stimulating hormone have been recorded in patients with both generalized tonic-clonic and partial seizures. Elevations of PRL and luteinizing hormone were seen immediately and at 20 minutes after generalized tonic-clonic seizures in male and female patients. Usually, PRL blood levels return to normal values within 1 hour. Previous studies have evaluated the utility of the transient increases in PRL, neuron-specific enolase, and S-100 protein as markers of epileptic seizures in children and adults. The conclusion was that measurement of serum PRL is a reliable confirmatory test in the presence of a seizure, but only modestly effective as a screening test for suspected seizures. Temporal lobe epilepsy is associated with abnormalities of reproductive physiology, but the mechanisms of hormonal dysregulation are not clear. A direct influence of epilepsy on the reproductive endocrine system is suggested by acute changes in PRL and gonadotropin levels following generalized and partial seizures, pointing to a possible relationship between temporolimbic epileptiform discharges and particular reproductive endocrine disorders. Chronic effects of the epileptic state and the acute impact of seizures could alter hypothalamic function, as indicated by downstream pulsatile secretion of luteinizing hormone. The brain controls reproductive function primarily through hypothalamic regulation of pituitary secretion regions of the hypothalamus. These are areas that are involved in the regulation, production, and secretion of gonadotropin-releasing hormone and receive extensive direct connections from the cerebral hemispheres, especially from temporolimbic structures, most notably from the amygdala, that are commonly involved in temporal lobe epilepsy. Significant relationships have been uncovered through which ictal and postictal effects of seizures and epilepsy may influence the function of this complex neuroendocrine system.

Interictal EEG discharges, reproductive hormones, and menstrual disorders in epilepsy

We evaluated reproductive endocrine function in women with unilateral temporolimbic epilepsy and normal control subjects to assess the effects of epilepsy, epilepsy laterality, and antiepileptic drug use on the cerebral regulation of hormonal secretion. The findings indicate that reproductive endocrine function differs between women with epilepsy and normal control subjects. Significant differences exist at all levels of the reproductive neuroendocrine axis, that is, hypothalamus, pituitary, and peripheral gland. Differences show significant relationships to the epilepsy itself as well as to medication use. Reproductive neuroendocrine changes occur in a stochastic manner such that the laterality of unilateral temporolimbic discharges is associated with predictable directional changes in hormonal secretion at all levels of the reproductive neuroendocrine axis. These directional changes are consistent with the finding that different reproductive disorders may develop in relation to left- and right-sided temporolimbic epilepsy. Hormonal changes can show close temporal relationship to the occurrence of interictal epileptiform discharges and may vary in relation to the laterality of the discharges. Antiepileptic drugs differ in their effects on reproductive hormone levels. There are notable differences between enzyme-inducing and noninducing drugs. Menstrual disorders are more common among women with interictal discharges as well as women with abnormal hormonal findings.

On the association between valproate and polycystic ovary syndrome

Recent studies by Isojärvi et al. have raised the issue of an increased incidence of polycystic ovary syndrome (PCOS) in women with epilepsy treated with valproate (VPA) and have proposed replacement with lamotrigine (LTG). Polycystic ovaries (PCO) are a common finding, with a prevalence >20% in the general population, and are easily detected by pelvic or vaginal ultrasonography, whereas PCOS is comparatively rare: few women with PCO have fully developed PCOS, which includes hirsutism, acne, obesity, hypofertility. hyperandrogenemia, and menstrual disorders. From an extensive review of the current literature, it appears that there are no reliable data on the actual prevalence of PCOS in normal women and in women with epilepsy. The pathogenesis of PCO is multifactorial, including genetic predisposition and the intervention of environmental factors, among which weight gain and hyperinsulinism with insulin resistance may play a part. The roles of central (hypothalamic/pituitary), peripheral, and local ovarian factors are still debated. PCO and PCOS appear to be more frequent in women with epilepsy, but there are no reliable data showing a greater prevalence after VPA. The recent studies by Isojärvi et al. may have been biased by the retrospective selection of patients. To date, there is no reason to contraindicate the use of VPA in women with epilepsy. However, patients should be informed about the risk of weight gain and its consequences.

Autonomic and hormonal ictal changes in gelastic seizures from hypothalamic hamartomas

OBJECTIVES

We describe two patients with hypothalamic hamartoma and gelastic seizures.

METHODS

We performed ictal neurophysiological studies with polygraphic recordings of autonomic parameters and hormonal ictal plasma concentration measurements.

RESULTS

Ictal recordings showed a stereotyped modification of autonomic parameters: increase in blood pressure and heart rate, peripheral vasoconstriction and modification of respiratory activity. At seizure onset, the norepinephrine plasma level was high and epinephrine unchanged, whereas prolactin and adrenocorticotropic hormone were increased in both cases. Growth hormone and cortisol plasma concentrations in each patient showed a different response to seizures.

CONCLUSIONS

These data provide evidence that gelastic seizures are accompanied by an abrupt sympathetic system activation, probably due to the direct paroxysmal activation of limbic and paralimbic structures or other autonomic centres of the hypothalamus and medulla.

Epilepsy and prolactin in adults: a clinical review

Serum levels of prolactin may increase as a consequence of epileptic seizures. The hormone release is caused by the propagation of epileptic activity, usually from the temporal lobe to the hypothalamic-pituitary axis. Due to the intensity of the epileptic afterdischarge, a rise is seen in approximately 60% of complex partial seizures. Prolactin usually fails to rise after psychogenic seizures, therefore, postictal prolactin levels can be used to differentiate between epileptic and psychogenic seizures. However, a subclassification of epileptic seizures by means of prolactin measurement is not possible. In repetitive seizures, prolactin may show a decrease in its postictal release. This is more common in status epilepticus, probably as a result of a diminished propagation of ictal activity during the course of status epilepticus. The influence of chronic epileptic discharges and anticonvulsant medication on prolactin release is moderate.

Serum prolactin levels and neonatal seizures

To assess the effects of neonatal seizures on the hypothalamus and to test clinical use of prolactin as a neonatal seizure marker, we studied postictal and recovery baseline serum prolactin levels in 19 neonates whose seizures were classified according to their clinical and EEG features. Postictal prolactin levels were obtained 30 min after the seizure, and recovery levels were ascertained 2-4 days later. The ratio of postictal prolactin level to recovery baseline level (prolactin ratio) was used as an indicator of postictal prolactin increase. The specificity and sensitivity of a prolactin ratio of > 2 was compared with the current standard of diagnosis (seizure discharges recorded by ictal EEG). Infants with electroclinical seizures had significantly higher prolactin ratios than control infants or infants with seizures without EEG correlation. Marked prolactin increases were noted only in infants with focal tonic seizures and temporal electrode involvement. A prolactin ratio of > 2 had a specificity of 100% and a sensitivity of 40%. We conclude that neonatal seizures have variable effects on the hypothalamus and that the low sensitivity and the need to await recovery levels limit the clinical value of prolactin ratio as a neonatal seizure marker.

Serum prolactin response to repetitive epileptic seizures

We measured postictal prolactin (PRL) levels during repetitive seizures in 14 patients (10 men and 4 women) suffering from epilepsy with focal and/or secondarily generalized seizures. Between two and six seizures occurred per patient (mean 2.7). The interveral between seizures was 15 min and 8 h 40 min (mean 3 h 32 min). Five of the 14 patients showed a marked postictal PRL rise after each seizure (i.e. concentrations above 700 microU/ml for women, 500 microU/ml for men). In the remaining 9 patients there was no detectable rise in PRL. A decrease in PRL did not occur in any of the 14 patients. In those patients who had shown a marked PRL increase after the first seizure, the PRL continued to rise in subsequent seizures. Unlike previous investigations, these results show that repetitive epileptic seizures are not necessarily followed by a decrease in postictal PRL levels. A decrease in PRL response is known to occur if there is progression to status epilepticus.

Growth hormone and prolactin in temporal lobe epilepsy

Growth hormone and prolactin levels were measured sequentially during wakefulness and sleep, in seven patients with unilateral temporal lobe epilepsy who underwent telemetric EEG monitoring (10-24 h), and in three additional patients studied while temporal structures were stimulated with implanted electrodes during pre-surgical evaluation. The results indicated that growth hormone/prolactin release patterns were not significantly affected by selective unilateral stimulation of deep temporal structures, or, when sleep patterns were normal, by epileptic activity confined to one temporal lobe.

Serum prolactin concentrations and epilepsy. A study which compares healthy subjects with a group of patients in presurgical evaluation and circadian variations with those related to seizures

In 20 healthy subjects (10 female and 10 male) and 17 patients undergoing presurgical epilepsy evaluation with intracranial EEG electrodes, circadian variations of serum prolactin (PRL) were measured. A comparison between the peak values found in normals with the postictal rises in patients, led us to consider 700 microU/ml to be the threshold of diagnostic value and the observed rises above this level to be all induced by seizures. In order to assess the clinical value of this threshold, PRL was measured postictally in a further 30 patients with epilepsy and in 11 patients with psychogenic seizures. In none of the latter group did PRL rises exceed 700 microU/ml, while they did so in 39% of the complex partial seizures and in 80% of the tonic-clonic seizures. There was no significant difference with respect to sex (a rise over 700 microU/ml in 42% in male and in 55% in female patients). Based on the findings in 17 patients investigated by means of intracranial electrodes, we were not able to establish different criteria for different focus localisations: in 66% of both temporal as well as frontal lobe seizures the 700 microU/ml level was exceeded. As a trend, in the period preceding an epileptic seizure we found a slightly decreasing PRL level, whereas in healthy persons the PRL concentrations gradually increased in the 40 minutes before the maximum spontaneous peak was reached.

The effect of seizures on hormones

Serum prolactin (HPR) levels are influenced by waking and sleep states, as reflected by surges in serum concentrations during daytime naps and nocturnal sleep. Other physiological causes of hyperprolactinemia include sexual activity, pregnancy, and lactation. Drugs may stimulate or inhibit HPR secretion. Pathological causes for HPR secretion include destructive lesions of the hypothalamus, prolactin-secreting neoplasms of the pituitary gland, lesions of the spinal cord, and occasionally Parkinson's disease. The most predictable postictal changes are increased serum cortisol levels and hyperprolactinemia. Serum HPR rises after virtually all generalized tonic-clonic seizures, most complex partial seizures, and some simple partial seizures. Absence and myoclonic seizures do not affect serum HPR levels. Repeated epileptic seizures and electroconvulsive therapy treatments produce successively less marked rises in serum HPR. The postictal elevation of serum cortisol has a longer latency than for HPR and follows an earlier rise in serum ACTH. Other postictal hormonal changes are much more variable. Because of the normal diurnal variation in serum cortisol levels and the relative delay in the postictal elevation of serum cortisol, HPR is more useful as a diagnostic measure of epileptic seizures. This application of HPR requires an understanding of other factors that influence serum HPR and the use of baseline serum HPR levels for comparison. HPR data must be correlated with behavioral and electroencephalographic events.

Activation of epileptic foci by transcranial magnetic stimulation: effects on secretion of prolactin and luteinizing hormone

Transient elevation of serum levels of prolactin has been observed following several types of epileptic seizures and after electrical stimulation of limbic temporal lobe structures via implanted electrodes. Transcranial magnetic stimulation has been found to selectively induce epileptiform afterdischarges in the epileptic focus of candidates for epilepsy surgery who suffered from temporal lobe epilepsy. Lateralized serial transcranial magnetic stimulation was therefore used and serum levels of prolactin or luteinizing hormone were measured to find if it could be used as a non-invasive diagnostic tool. The investigation was performed on six patients and five healthy volunteers. In the patients the induction of epileptiform potentials was continuously monitored via subdural electrodes. A transient surge of prolactin and luteinizing hormone was found in only one patient, in whom a complex partial seizure was induced. Thus, transcranial magnetic stimulation appeared not to be helpful for the lateralization of the (primary) epileptic focus during presurgical evaluation.

A hypothesis to integrate partial seizures of temporal lobe origin and reproductive endocrine disorders

Recent demonstrations of an association between reproductive endocrine disorders and partial seizures of temporal lobe origin (TLE) have led to the following hypothesis: (1) TLE may promote the development of reproductive endocrine disorders, (2) reproductive endocrine disorders may promote the development of epileptic discharges, and (3) TLE and associated reproductive endocrine disorders may represent the parallel effects of prenatal factors which are common to the development of both the brain and the reproductive system. This article focuses on clinical and animal investigative data that form the basis of this hypothesis.

Differential response of growth hormone, cortisol, and prolactin to seizures and to stress

Plasma concentrations of growth hormone (GH), cortisol, and prolactin (PRL), following a spontaneous generalized seizure in epileptic men were compared with similar measurements made in nonepileptic, stressed men to determine the role of stress in the hormonal response to seizures. Nonepileptic, nonstressed men served as control subjects. GH concentrations increased significantly within 60 min postictally, and as expected, so did cortisol and PRL. A subgroup of alcoholic patients exhibited a smaller GH response to seizures. Stressed patients had significantly less elevated cortisol and PRL plasma values, but no rise of GH. The data suggest that neurogenic stimuli responsible for the postictal release of GH, cortisol, and PRL are, at least in part, independent of stress mechanisms and that GH response is blunted in alcoholic patients.

Intravenous procaine as a probe of limbic system activity in psychiatric patients and normal controls

Evidence from animal and human studies suggests that procaine hydrochloride may selectively activate limbic system structures and suppress neocortical structures. We administered a series of intravenous bolus doses of procaine hydrochloride to 31 subjects (7 with affective disorders, 17 with borderline personality disorder, and 7 healthy normal volunteers). Dose-related cognitive and sensory distortions and illusions were observed; affective experiences ranged widely from euphoric to dysphoric. Topographic electroencephalogram (EEG) analysis indicated selective increases in fast activity (26-45 Hz) over the temporal lobes; the degree of increase in this activity correlated with degree of dysphoria experienced. Procaine was associated with increases in secretion of cortisol, adrenocorticotrophic hormone (ACTH), and prolactin, but not with growth hormone. These preliminary data are consistent with the possibility that procaine might serve as a clinically useful probe of psychosensory, affective, electrophysiological, and endocrine effects referable to the limbic system.

Neuroendocrine effects of limbic activation by electrical, spontaneous, and pharmacological modes: relevance to the pathophysiology of affective dysregulation in psychiatric disorders

1. Literature is reviewed that implicates various limbic structures (particularly amygdala and hippocampus) in the modulation of stress-associated neuroendocrine systems. 2. Procaine and related local anesthetics may show a selective proclivity for activating limbic structures. 3. Procaine stimulates ACTH-cortisol and prolactin, but not growth hormone secretion. This pattern is most comparable to that elicited by stimuli which act bilaterally on temporal lobe and limbic areas. 4. Procaine may be a useful agent for helping to elucidate the anatomic and physiologic basis for mood, endocrine, and cognitive dysregulation associated with stress and affective disorders. 5. The endocrine concomitants of limbic activation may have relevance to the course and symptom complex of affective disorders and related psychiatric conditions.

The effect of limbic and extralimbic electrical stimulations upon prolactin secretion in humans

The effect that extra-hypothalamic regions of the brain have upon prolactin secretion in humans was evaluated by performing electrical stimulations. Thirty-nine stimulations were performed, 22 to basolateral amygdala, 12 to hippocampus and 5 to orbitofrontal, supplementary motor and cingulate cortex. Only two stimulations causing high-frequency widespread limbic afterdischarges were followed by significant prolactin elevation. Four low-frequency afterdischarges involving amygdala and anterior hippocampus, one amygdala stimulus-dependent discharge and 19 amygdala, 8 hippocampal and 5 frontal sub-afterdischarge threshold stimulations had no prolactin elevation. These results fail to replicate earlier studies. We suggest that there is no evidence that the amygdala regulates serum prolactin within physiologic ranges, but that the regulation of prolactin may depend primarily upon other sub-cortical structures.

Serum prolactin and cortisol levels in evaluation of pseudoepileptic seizures

In 6 patients with epilepsy, a twofold increase in serum prolactin levels followed true epileptic seizures, but no significant change followed pseudoepileptic attacks in 6 other patients. Serum prolactin concentration is a useful biochemical marker to distinguish between epileptic and pseudoepileptic seizures. Serum cortisol levels also increased after epileptic seizures, but diurnal and individual variations render the cortisol level a less reliable indicator of such attacks.

Autonomic nervous system and epilepsy

Seizures frequently manifest autonomic dysfunction clinically, and seizure discharges commonly spread into and involve autonomic pathways. These associations are direct and simple in some instances, and the result of multiple indirect and complex relationships in others. Effects of epileptic discharge on the autonomic nervous system are mediated through the cortical, limbic, and hypothalamic systems. Some significant consequences of altered autonomic function include convulsive apnea, abnormal sexual function, and potentially fatal effects on the cardiovascular system.

Paramethasone acetate (PA): corticosteroid potency vs hypothalamic pituitary-gonadal axis

Because paramethasone acetate (PA) suppresses basal and midcycle LH surge and blocks estrogen synthesis in the female, its possible effect upon testicular physiology was evaluated in 13 healthy men by measuring the circulating levels of FSH, LH, prolactin (PRL), testosterone (T), dihydrotestosterone (DHT), androstenedione (A), estradiol (E2) and cortisol (C) every 4 h throughout the day, before (control) and after PA (6 mg/d/7 d). The total concentrations of each hormone, as well as the PA-induced suppressibility (measured as percent decrease in the mean 24 h plasma level) were analyzed. PA suppressed neither the basal nor circadian rhythm of T and had no effect on LH, FSH or PRL output. DHT, A, E2 were significantly reduced and the basal concentrations and circadian variations of C were abolished. PA showed a dual control on the pituitary gonadal axis and while causing a maximal suppressed adrenocortical activity it had no interference in testosterone synthesis.

Endocrine function following complex partial seizures

Previous studies have demonstrated hyperprolactinemia following generalized tonic-clonic seizures and after electroconvulsive therapy. We found transient hyperprolactinemia following complex partial seizures but little change in serum gonadotropins, thyroid-stimulating hormone, growth hormone, or cortisol. Serum prolactin was invariably normal interictally. Postictal elevation of serum prolactin may represent a biochemical marker of complex partial seizures, and it offers a potential pathogenic mechanism for the sexual dysfunction that often complicates temporal lobe epilepsy.

Diurnal variations of pituitary and testicular hormones in paraplegic men

The effect of the neuro-spinal cord injury upon testicular physiology was evaluated in six adult paraplegic (PPG) men by measuring the circulating levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), androstenedione, testosterone, and dihydrotestosterone every 4 hr throughout a 24-hr period. Three PPG men were studied within the first 3 months (acute period) and the other three patients 39-79 months (stabilized period) after trauma. Hormonal values were compared with eight age-matched normal adult males. Plasma FSH and LH were constantly above normal concentrations regardless of the sampling time and period of observation, whereas prolactin was higher than normal only during the first two months after trauma, returning to normal afterwards. Plasma androgens were consistently below normal during the first 3 months after injury, and returned toward normal thereafter. There may be a direct relationship between the time elapsed after the spinal cord injury and the plasma androgens concentrations. A possible role of PRL in testicular steroidogenesis is suggested.