puberty measures

Puberty and Its Measurement: A Decade in Review

Measuring Puberty

A commonly used measure of puberty is Tanner Stage. Tanner staging categorizes individuals along an ordinal puberty scale from 1 to 5, on the basis of pubic hair and breast development in females, and pubic hair and genital development in males [Tanner, 1971; Tanner and Whitehouse, 1976]. Tanner staging by physical exam should be carried out by a trained clinician. There are several limitations to Tanner staging. The scale was developed with reference to a single ethnic group (there may be cross-ethnic differences) and in a relatively small sample of 200 children. Overweight girls will tend to be inaccurately staged, due to the reliance of the staging on breast development, which can be erroneously over-estimated in a purely visual examination. Despite these limitations, Tanner staging has historically been considered the gold standard for puberty measurement [Dorn, 2006].

In light of the above-mentioned concerns, it might be expected that Tanner staging by physical examination could be usefully supplemented by hormonal assays, since these measure adrenal and gonadal (or adrenal/gonadal-releasing) hormones upstream from their external physical effects. Hormone assays may be increasingly useful for measuring pubertal stage in the future; however, at the present time it is unclear how hormone measurements should be combined with (or used in conjunction with) other measures such as Tanner stages [see Shirtcliffe et al., 2009]. There are also other practical issues regarding hormonal measures, including cost, subject burden, and the fact that levels of different puberty hormones fluctuate in monthly and circadian cycles. Little research has been done comparing hormone levels in different biological samples (saliva, blood, urine) with clinician-assessed Tanner stages [see Dorn, 2006; Shirtcliffe et al., 2009], so it is unclear how much weight should be given to hormone levels. At a conceptual level, for example, some neurobehavioral changes at puberty may be the direct result of increasing hormone levels on specific neural systems during adolescent brain development (and thus best quantified by hormone measures) while other neurobehavioral changes may reflect more complex influences (e.g. changes in social experience that are more directly tied to the physical changes and social roles, and better linked to Tanner stages than any specific hormone change).

The Role of Puberty in the Developing Adolescent Brain

Tanner staging by physical examination by a qualified clinician can raise practical issues regarding appropriateness and convenience. Often this is best accomplished in the context of doing a brief “health” exam. That is, Tanner staging can be part of a normal physical health exam and therefore should not be associated with any stigma or ethical concerns (beyond a normal physical health check). However, the cost (clinician time, special room and equipment for a physical exam, and explaining the procedures to the adolescent and family) can make this impractical for many research studies. Therefore, it is valuable to consider alternative ways to quantify pubertal maturation, such as assessments by self-report questionnaire. A relatively large number of studies have assessed self-rated (or parent-rated) Tanner stage using the Petersen Development Scale [PDS; Petersen et al., 1988]. This is a questionnaire that includes items assessing hair growth, skin changes, and growth spurt, with sex-specific items i.e. menarche and breast development in females, and genital growth and facial hair in males. As such, the PDS measures a composite puberty score that includes the effects of adrenal and growth hormones, as well as gonadal hormones. Correlations with clinician-assessed Tanner stage are not especially high: one study found correlations between 0.61 and 0.67 in 11- to 13-year-old girls for the self-report PDS [Brooks-Gunn et al., 1987; correlations are even lower for parent-report PDS; see Shirtcliffe et al. 2009]. The extent to which these relatively low correlations are due to inaccurate self-rating, or to distinct constructs, such as the distinct effects of adrenal/growth versus gonadal hormones, needs to be evaluated. The PDS can be used with caution to estimate Tanner stage when a physical examination is not possible. However, if the research question does not concern hormone levels and Tanner stage, but instead relates to self-image and self-consciousness, or to puberty stage relative to peers, it can be argued that the PDS is the most relevant measure [see Dorn, 2006 for discussion]. In summary, researchers should give ample consideration to which aspect of puberty is most relevant to their research question and select their measures of puberty (and overall design of the study) accordingly.