Hormones in human behaviour

Hormones in human behaviour

Media Watch Hormones in human behaviour How and why are men and women different? How are the differences influenced by nature and by nurture? As Baron...

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Media Watch

Hormones in human behaviour How and why are men and women different? How are the differences influenced by nature and by nurture? As BaronCohen, Lutchmaya, and Knickmeyer contemplate, some of the differences might be due to sex hormones present during fetal development. Research studies in human beings confirm the findings of studies in other species: processes that guide the development of the genitalia also affect the brain and behaviour. High doses of androgens early in fetal life cause the growth of the penis and scrotum; these hormones seem to promote the development of “male-typical” behaviour and inhibit the development of “female-typical” behaviour. We know this mainly from study of females with congenital adrenal hyperplasia (CAH), whose prenatal androgen concentrations were very high. For example, girls with CAH prefer to play with boys’ toys and report interest in maletypical occupations, such as airline pilot; girls and women with CAH seem to have better spatial ability than those without CAH. These behavioural effects of prenatal androgen coexist with female gender identity. But, CAH is not a perfect experiment because girls with the disorder have masculinised genitalia and very high concentrations of androgen. So, increasingly, researchers have sought to confirm the behavioural effects of hormones in healthy people. One approach—relating hormones in a mother’s blood during pregnancy to her offspring’s behaviour—showed that mothers with high testosterone concentrations were more

likely than mothers with low testosterone concentrations to have daughters interested in boys’ activities. Researchers hoping to measure hormones in the fetus itself assess amniotic fluid. This is the method used by Baron-Cohen and colleagues, with mixed but mostly negative results. It is difficult to know what to make of failures to find within-sex associations between amniotic testosterone and later behaviour. Is behaviour unaffected by prenatal hormones within the normal range? Or, more likely, are amniotic studies inherently restricted by small samples (and low statistical power) and a single sample of testosterone (which may not be representative of the fetus’ continuing exposure)? The authors are to be commended for tackling such a difficult study and for calling attention to the topic, but their results do not create a compelling story. The authors also miss an opportunity to educate and engage readers, most of whom would pay good money to know why the sexes differ. Important historical and contemporary studies are neglected; the research covered is unusually selective and dated, with over-reliance on secondary sources. Regrettably, the energy and productivity that characterise study of the effects of hormones on human behaviour are not captured in this book.

Prenatal Testosterone in Mind: Amniotic Fluid Studies Simon Baron-Cohen, Svetlana Lutchmaya, Rebecca Knickmeyer MIT Press, 2004 £19·95, 131 pages ISBN 0 262 02563 9

Sheri A Berenbaum [email protected]

Case-based learning will travel John Noseworthy and his peers from the Mayo Clinic have assembled case-reports of 50 interesting patients with a range of neurological disorders, “to teach and entertain”. Both objectives are met in his well-priced, pocket-sized, paperback book, which has a very attractive layout and reads like a novel. Each case-report starts with a narrative of how the patient developed symptoms, what deficits were found on neurological assessment, and the results of ancillary assessments. From this information, the reader should deduce the diagnosis. This is revealed to the reader over the page, and a very useful commentary written by an expert from the Mayo Clinic follows. The commentary does not only cover differential diagnoses, but also provides a concise and up-to-date survey of the specific diagnostic entity. The quality of the illustrations is excellent. Although the clinical discussions are brief and accompanied by only one reference, there is something to learn from each report. However, the choice of cases is haphazard; some of the diseases are uncommon in clinical practice. Most of us will http://neurology.thelancet.com Vol 4 June 2005

probably never encounter a patient with chronic-infantileneurological-cutaneous and articular/neonatal-onset multisystem-inflammatory disease or adult-polyglucosanbody disease. It would be silly, on my part, to give away the diagnoses of the other 48 cases, but I can assure you that most of the case-reports are straightforward, covering patients with disorders that are relevant to most practising neurologists. Overall, it is hard to find much wrong with this book, except perhaps for the index, which is redundant. In my opinion the book is intended mostly for neurologists and neurologists-in-training, and is less suitable for medical students who are new to neurology. Fifty Neurologic Cases from Mayo Clinic is a delightful book to dip into. It is suited to reading on the bus, train, airplane, or while waiting in the lounge for your next flight, and it would be a perfect gift for a colleague whatever the occasion.

Fifty Neurologic Cases from Mayo Clinic Edited by John H Noseworthy Oxford University Press, 2004 £24·95, 218 pages ISBN 0 19 517745 2

Jacques De Keyser [email protected]