Constitutional short stature is a medical term which refers to short standing height (Stature). But how is “short” medically defined, or, in other words, what constitutes “Short Stature”?
Well, it has been agreed by consensus that constitutional short stature is a condition in which the height of an individual is more than 2 standard deviations (SD) below the corresponding mean height for a given age, sex, and population group without evidence of systemic, endocrine, nutritional, or genetic diseases [1,2,3].
In order to better understand what that means, let’s elaborate further on standard deviation and the mean height.
When assessing distribution of height in a population, we observe that it follows the normal Bell curve (Fig 1). This means the majority of the individuals of the population are closer to the mean average height (peak of the curve) and progressively fewer numbers of individuals have shorter or taller (deviation) height than that average height. In fig. 1, we see that the average height is approximately 5’4” in females and 5’10” in males. The mean value varies between human races; the chart refers to Caucasians.
In statistics, one standard deviation (1 SD) away from the mean value (in our case the mean height) in either direction on the horizontal axis (the two shaded areas closest to the peak of the curve on the graph of fig 2.) accounts for approximately 68 percent of the people (fig 2). Two standard deviations away from the mean (the four areas closest to the peak) account for roughly 96 percent of the people.
Normal height is considered any height within 2 standard deviations (SD) from the mean. Short stature is any height below – 2SD. In Caucasian populations, the lower limit of so-called “normal stature” is 5’5” (166cm) for males and 5’0” (153cm) for females.
1. Cohen P, Rogol AD, Deal CL, et al. Consensus statement on the diagnosis and treatment of children with idiopathic short stature: a summary of the Growth Hormone Research Society, the Lawson Wilkins Pediatric Endocrine Society, and the European Society for Paediatric Endocrinology Workshop. J Clin Endocrinol Metab. 2008 Nov. 93(11):4210-7.
2. Ranke MB. Towards a consensus on the definition of idiopathic short stature. Horm Res 1996 45(Suppl 2):64–66
3. .Sultan M, Afzal M, Qureshi SM, et al. Etiology of short stature in children. J Coll Physicians Surg Pak. 2008 Aug. 18(8):493-7.