Tall stature is most commonly familial in origin and considered a sign of good health. On rare occasions, however, taller than otherwise expected stature may arise as a consequence of a disorder or syndrome. These can be categorized as either chromosome disorders, genetic disorders, or endocrine disorders. The following summary of somewhat rare height related disorders is merely for raising awareness. For anything more than that, specialists such as geneticists, endocrinologists, and pediatricians should be consulted. If you want to do some research on your own, you might start with the following two open access articles:
- Investigation and management of tall stature
- Tall stature in children: differential diagnosis and management
Humans typically have 23 pairs of chromosomes with the final pair consisting of either an XX (female) or XY (male) chromosome combination. Occasionally, however, the male sperm and/or female egg may transfer additional X or Y chromosomes. There are many variants, but the most common are trisomies: XXX in females and XYY and XXY (Klinefelter) in males, all of which tend to coincide with taller stature than would otherwise be expected. It is thought that this is caused by increased gene dosage which results from the extra SHOX gene in the additional chromosomes . XXX and XYY syndromes have a 1 in 1000 prevalence and are infrequently diagnosed as symptoms are mild and rarely noticeable.
Klinefelter syndrome (XYY) occurs slightly more frequently, closer to 1 in 500 males . Those with Klinefelter are usually considered male and are usually infertile due to diminished functionality of the testes. Klinefelter is diagnosed via analysis of the chromosomes and prognosis is good with reports of normal, independent lives shortened by only a few years. More rare cases of chromosomal sex disorders result from four or more sex chromosomes and can also result in increased stature. A geneticist should be consulted if a chromosome disorder is suspected.
Other Genetic Disorders
Besides abnormal number of chromosomes, there are other genetic disorders that can cause tall stature. Marfan’s Syndrome is the most well-known. It affects human connective tissue and commonly presents with long slender limbs, fingers, and toes. There are many other possible signs and symptoms, from abnormalities of the skeletal system (scoliosis, pectus excavatum, excessive joint flexibility, etc.) to problems with the cardiovascular system, eyes, lungs, and central nervous system. It is diagnosed when multiple of these symptoms are present and management is of the symptoms. Prognosis has improved considerably in recent years to nearly full life expectancy. However, if left untreated, it can be life threatening. The Marfan Foundation cites an estimate that roughly half of people with Marfan’s syndrome don’t know they have it. Listed below are some other height related genetic disorders which are sometimes referred to as overgrowth syndromes:
The endocrine consists of the glands that deliver hormones to other organs in the body via direct secretion into the circulatory system. The pituitary, kidneys, and thyroid glands often play a role in height related disorders, including the following:
- Growth Hormone Disorders – Excess HGH is secreted by the pituitary gland. Most often this is due to a benign (non-cancerous tumor). This excess hormone increases rate of growth. When it occurs during childhood, it may result in Gigantism. The term Gigantism is normally reserved for more than three standard deviations above normal height. When excess hormone occurs after puberty, the condition is known as Acromegaly. Often, large hands, face, and feet are present with Gigantism. The most famous case of Gigantism is that of Robert Wadlow.
- Delayed or Advanced (Precosious) Puberty – The androgen (including testosterone) and estrogen sex hormones secreted by the testicles and ovaries affect growth hormone production as well as the onset and duration of puberty. High levels of sex hormones may cause an early (precocious) puberty, and thereby early tall stature followed by stunted growth. Low levels of sex hormone may delay puberty, allowing the growth plates to remain open longer and resulting in tall adult stature .
- Hyperthyroidism – The thyroid is a butterfly-shaped gland in the neck that is responsible for regulating hormone sensitivity, energy usage, and protein fabrication. Essentially, it helps regulate the rate of living. Hyperthyroidism refers to the state where the thyroid is overactive and producing excessive T3 and T4 hormones. These in turn can trigger increased growth hormone production, leading to tall stature. The common test is to check the levels of thyroid stimulating hormone (TSH) the pituitary uses to regulate the thyroid.
All of the syndromes and disorders listed on this page are rare. However, if one is suspected, a GP, or an appropriate specialist such as an endocrinologist, pediatrician, or geneticist should be consulted.