EEG and the Effects of Hormone Treatment

The administration of hormone replacement therapy (HRT) offers the promise of normalization of function, but EEG/ERP has been used to determine whether general brain state or cognitive function indeed improved with treatment. Schneider and colleagues (2005) examined the effects of growth hormone (GH) replacement deficiency on the sleep EEG, using polysomnography in growth hormone-deficient patients. Results showed that the values for the obtained sleep parameters were similar to those for healthy individuals as reported in the literature and therefore, the authors conclude that 6 months of GH replacement therapy did not adversely affect night sleep or daytime sleep propensity (Schneider et al, 2005).

Golgeli and colleagues (2004) examined the effects of growth hormone (GH) replacement therapy on cognitive function in women with Sheehan's syndrome. Sheehan's syndrome is also known as postpartum hypopituitarism, a pituitary hormone deficiency as a result of life-threatening blood loss during or after childbirth. At baseline, amplitude and latencies of auditory oddball ERPs of patients showed longer latencies than those of controls. After 6 months of hormone replacement therapy, patients showed decreased P300 latencies compared to pre-treatment levels. The authors conclude that Sheehan's syndrome is associated with cognitive impairment as demonstrated by prolonged P300 latencies and the improvement with GH replacement. The conclusions of this study could have been strengthened if the paper had reported EEG measures in the control group as well, after a 6-month period.

In a similar study on the effects of thy-roxine treatment in congenital hypothyroidism, Oerbeck and colleagues (2007), in a cross-sectional paradigm, used an auditory oddball paradigm to examine P300 and earlier cognitive (P1, N1, P2) ERP components. Significant group differences in amplitude and latency were found on early ERP components (P1, N1). P300 latency and amplitude in the congenital hypothy-roidism group were negatively correlated with duration of treatment. The authors interpret these findings as suggesting that early treatment may have helped to normalize the P300 component.

These studies demonstrate the potential added value of EEG to examine treatment effects; principally the ability to register subtle changes in brain processing that may not be evident on performance tests. Most of the studies reviewed above examine the effects of treatment on the P300. Some of the paradigms above involve before and after measurements of the P300, assuming that changes in the P300 will reflect changes in treatment, an assumption which may be questionable in the absence of control group comparisons. The P300 component is strongly affected by state, and control of this factor is essential for interpretation of treatment effects.

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