Short stature refers to a height of a human being which is below expected. In medical context, short stature represents the shortest 2,3% of individuals. Shortness in children and young adults nearly always results from below-average growth in childhood, whereas acquired shortness in older adults is usually caused by degenerative changes of the spine.
Short stature can be due to various etiologies and the cause may be a primary or secondary growth disorder, or idiopathic (without a known cause).
Primary growth disorders are intrinsic to the growth plate and include clinically defined syndromes, factors that result in being born small for gestational age (SGA), and skeletal dysplasias. Secondary growth disorders are believed to change the milieu of the growth plate and include GH deficiency, disorders of the GH–insulin-like growth factor (IGF)-I axis (Pic. 1) including IGF-I deficiency or resistance, endocrine and metabolic disorders, organ system disorders, malnutrition, psychosocial disorders, and iatrogenic conditions (certain treatments or drugs). Patients with idiopathic short stature (ISS) have no discernible cause, the condition is very heterogeneous and may be either familial or non-familial. In all cases, an early diagnosis is important and, therefore, height screening programs must be sufficiently sensitive and specific to ensure timely detection and treatment.
While the short stature caused by malnutrition, hormonal deficiencies, drug administration or chronic diseases is proportionate, most of skeletal dysplasias cause disproportionate short stature. One of them, achondroplasia (Pic. 2) a common cause of dwarfism, typically causes short limbs but relatively normally-sized head and torso.
For several diagnoses causing short stature, therapy with growth hormone (GH) has been approved. Efficacy of GH treatment is better when started at a young age, and diagnosis should, therefore, be made as early as possible. The administration of GH treatment usually results increase in final height of about 5 to 10 cm, but the outcome depends on the cause.
Out of all possible causes of short stature, two conditions causing also a short stature are strongly associated with fertility issues, Turner syndrome and Prader-Willi syndrome:
Turner's syndrome is a genetic disorder that affects only females. Turner syndrome is caused by a chromosomal abnormality in which all or part of one of the X chromosomes is missing or altered. While most people have 46 chromosomes, people with TS usually only have 45. The most common features in young infants are swollen hands and feet, drooping eyelids, spots of skin, and a wide or web-like neck. Other symptoms during childhood may include stunted growth, a flat chest shaped like a shield, incomplete or absent development at puberty, and an early loss of ovarian function and menstrual cycle. Due to the loss of ovarian function, many girls do not start their periods or develop breasts. Women with Turner syndrome are almost universally infertile since TS is characterized by primary amenorrhoea (absence of menstrual cycles without any previous menstruation) premature ovarian failure and streak gonads.
Prader–Willi syndrome (PWS, Pic. 3) is a genetic disorder due to loss of function of specific genes on chromosome 15. The syndrome shows great variability, with changing clinical features during a patient’s life. A newborn might suffer from severe hypotonia (reduced muscle tone) with feeding problems and global developmental delay. During infancy these characteristics impede the acquisition of gross motor and language milestones. A PW child develops hyperphagia (overfeeding) during the initial stage of infancy that can lead to precocious obesity if left uncontrolled. This is most probably caused by a hypothalamic dysfunction, which impedes the sense of satiety. This hypothalamic dysfunction is also responsible for growth-hormone (GH) and thyroid-stimulating hormone (TSH) deficiencies (leading to short stature and hypothyreoidism), central adrenal insufficiency, and hypogonadism (failure of the sex glands). During infancy, the PW child shows a characteristic problematic behavioral pattern, which has been reported to worsen with age. Patients sometimes present psychosis.