Sports Endocrinology

SportsEndocrinologyWordCloud

The Endocrine system comprises various glands distributed throughout the body that secrete hormones to circulate in the blood stream. These chemical messengers, have effects on a vast range of tissue types, organs and therefore regulate metabolic and physiological processes occurring in systems throughout the body.

The various hormones produced by the Endocrine system do not work in isolation; they have interactive network effects. The magnitude of influence of a hormone is largely determined by its circulating concentration. This in turn is regulated by feedback loops. For example, too much circulating hormone will have negative feedback effect causing the control-releasing system to down regulate, which will in turn bring the level of the circulating hormone back into range. Ovulation in the menstrual cycle is a rare example of a process induced by positive hormonal feedback.

In the control system of hormone release, there are interactions with other inputs in addition to the circulating concentration of the hormone. The hypothalamus (gland in the brain) is a key gateway in the neuro-endocrine system, coordinating inputs from many sources to regulate output of the pituitary gland, which produces the major stimulating hormones to act on the Endocrine glands throughout the body.

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The Endocrine system displays complex dynamics. There are temporal variations in secretion of hormones both in the long term during an individual’s lifetime and on shorter timescales, as seen in the diurnal variation of some hormones such as cortisol, displaying a circadian rhythm of secretion. The most fascinating and complex control system is found in the hypothalamic-pituitary-ovarian axis. Variation in both frequency and amplitude of gonadotrophin releasing factor (GnRH) secretion from the hypothalamus dictates initiation of menarche and the subsequent distinct pattern of cyclical patterns of the sex steroids, oestrogen and progesterone.

So what have the Endocrine system and hormone production got to do with athletes and sport performance?

  1. Exercise training stimulates release of certain hormones that support favourable adaptive changes. For example, exercise is a major stimulus of growth hormone, whose action positively affects body composition in terms of lean mass, bone density and reduction of visceral fat.
  2. Disruption of hormones secreted from the Endocrine system can impair sport performance and have potential long term adverse health risks for athletes. This picture is seen in the female athlete triad (disordered eating, amenorrhoea and low bone mineral density) and relative energy deficiency in sport (RED-S) with multi-system effects. In this situation there is a mismatch between dietary energy intake (including diet quality) and energy expenditure through training. The net result is a shift to an energy saving mode in the Endocrine system, which impedes both improvement in sport performance and health. RED-S should certainly be considered among the potential causes of sport underperformance, suboptimal health and recurrent injury,  with appropriate medical support being provided.
  3. Caution! Athletic hypothalamic amenorrhoea, as seen in female athletes (in female athlete triad and RED-S) is a diagnosis of exclusion. Other causes of secondary amenorrhoea (cessation of periods >6 months) should be excluded such as pregnancy, polycystic ovary syndrome (PCOS), prolactinoma, ovarian failure and primary thyroid dysfunction.
  4. Unfortunately the beneficial effects of some hormones on sport performance are misused in the case of doping with growth hormone, erythropoeitin (EPO) and anabolic steroids. Excess administered exogenous hormones not only disrupt the normal control feedback loops, but have very serious health risks, which are seen in disease states of excess endogenous hormone secretion.

So the Endocrine system and the circulating hormones are key players not only in supporting health, but in determining sport performance in athletes.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance

References

Sport Performance and RED-S, insights from recent Annual Sport and Exercise Medicine and Innovations in Sport and Exercise Nutrition Conferences Dr N. Keay, British Journal of Sports Medicine 17/3/17

Teaching module on RED-S for British Association of Sport and Exercise Medicine as CPD for Sports Physicians

Optimal Health: Including Female Athletes! Part 1 – Bones Dr N. Keay, British Journal of Sport Medicine 26/3/17

Optimal Health: Including Male Athletes! Part 2 – REDs Dr N. Keay, British Journal of Sport Medicine 4/4/17

Optimal health: especially young athletes! Part 3 Consequences of Relative Energy Deficiency in sports Dr N. Keay, British Association of Sport and Exercise Medicine 13/4/17

Optimal health: for all athletes! Part 4 Mechanisms Dr N. Keay, British Association of Sport and Exercise Medicine 13/4/17

Enhancing sport performance: part 1 Dr N. Keay, British Association of Sport and Exercise Medicine

Enhancing sports performance: part 3

From population based norms to personalised medicine: Health, Fitness, Sports Performance Dr N. Keay, British Journal of Sport Medicine

Sleep for health and sports performance Dr N. Keay, British Journal of Sport Medicine

Balance of recovery and adaptation for sports performance Dr N. Keay, British Association of Sport and Exercise Medicine

Clusters of athletes Dr N. Keay, British Association of Sport and Exercise Medicine

Inflammation: why and how much? Dr N. Keay, British Association of Sport and Exercise Medicine

Fatigue, Sport Performance and Hormones…Dr N. Keay, British Journal of Sport Medicine

Keay N, Logobardi S, Ehrnborg C, Cittadini A, Rosen T, Healy ML, Dall R, Bassett E, Pentecost C, Powrie J, Boroujerdi M, Jorgensen JOL, Sacca L. Growth hormone (GH) effects on bone and collagen turnover in healthy adults and its potential as a marker of GH abuse in sport: a double blind, placebo controlled study. Journal of Endocrinology and Metabolism. 85 (4) 1505-1512. 2000.

Wallace J, Cuneo R, Keay N, Sonksen P. Responses of markers of bone and collagen turover to exercise, growth hormone (GH) administration and GH withdrawal in trained adult males. Journal of Endocrinology and Metabolism 2000. 85 (1): 124-33.

Keay N. The effects of growth hormone misuse/abuse. Use and abuse of hormonal agents: Sport 1999. Vol 7, no 3, 11-12.

Wallace J, Cuneo R, Baxter R, Orskov H, Keay N, Sonksen P. Responses of the growth hormone (GH) and insulin-like factor axis to exercise,GH administration and GH withdrawal in trained adult males: a potential test for GH abuse in sport. Journal of Endocrinology and Metabolism 1999. 84 (10): 3591-601.

Keay N, Logobardi S, Ehrnborg C, Cittadini A, Rosen T, Healy ML, Dall R, Bassett E, Pentecost C, Powrie J, Boroujerdi M, Jorgensen JOL, Sacca L. Growth hormone (GH) effects on bone and collagen turnover in healthy adults and its potential usefulness as in the detection of GH abuse in sport: a double blind, placebo controlled study. Endocrine Society Conference 1999.

Wallace J, Cuneo R, Keay N. Bone markers and growth hormone abuse in athletes. Growth hormone and IGF Research, vol 8: 4: 348.

Keay N, Fogelman I, Blake G. Effects of dance training on development,endocrine status and bone mineral density in young girls.Current Research in Osteoporosis and bone mineral measurement 103, June 1998.

Keay N, Effects of dance training on development, endocrine status and bone mineral density in young girls, Journal of Endocrinology, November 1997, vol 155, OC15.

Keay N, Fogelman I, Blake G. Bone mineral density in professional female dancers. British Journal of Sports Medicine, vol 31 no2, 143-7, June 1997.

Keay N. Bone mineral density in professional female dancers. IOC World Congress on Sports Sciences. October 1997.

Keay N, Bone Mineral Density in Professional Female Dancers, Journal of Endocrinology, November 1996, volume 151, supplement p5.

From population based norms to personalised medicine: Health, Fitness, Sports Performance

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“Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”. World Health Organisation 1948

There has been criticism of this definition, arguing that the word “complete” has opened the door to today’s more medicalised society. However, this trend coincides with increased volume of “patients” seeking optimal health, together with doctors who have a more extensive repertoire of medical interventions at their disposal. In a time-pressed society there is less opportunity for either patient or doctor to explore longer term adaptive measures and prevention strategies, which facilitate taking responsibility for your health. Fortunately Sport and Exercise Medicine became a recognised medical specialty in the UK in 2006. This encompasses population-based strategies for disease prevention outlined in the global initiative founded in 2007 “Exercise is Medicine“.

What has this got to do with sports performance? There are subgroups within the population, such as athletes already taking plenty of exercise. Elite athletes differ from the general population, due to superior adaptation processes to exercise, probably with a genetic component. So are the same “normal” population-based ranges of quantified medical parameters applicable?

This is precisely the issue that arose when I was on the international medical research team investigating the development of a dope test for growth hormone (GH). Crucially, exercise is one of the major stimuli for growth hormone release from the anterior pituitary. So before we could even start investigating potential downstream markers of exogenous GH abuse, the “normal” range for elite athletes had to be established.

In a similar way, are the “normal” ranges for other hormones applicable to athletes? In a fascinating lecture delivered by Dr Kristien Boelaert, Consultant Endocrinologist, it was explained that the distribution for thyroid stimulating hormone (TSH) is affected by multiple factors, including illness, age and exercise status. So “normal” for the general population is not necessarily normal for specific subgroups.

The other issue, especially with the Endocrine system is that hormones act on a variety of tissues and so produce a variety of multi-system network effects with interactions and control feedback loops. Therefore symptoms of malfunction/maladaptation and subclinical conditions can be non specific. From a doctor’s perspective this makes Endocrinology fascinating detective work, but challenging when dealing with subgroups in the population who require a more intensive work-up and individualised approach.

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The vast majority of research studies involve exclusively male athletes, leaving female athletes under-represented (a recent study on heat adaptation in female athletes being a notable exception). Some areas of research, including my own, have been directed more towards female athletes in the case of female athlete triad, or Relative Energy Deficiency in sports (REDs). REDs is a more appropriate term as it really sums up the important points: male and female can both be affected and therefore should both be studied. There are subgroups within the general population who may not fit the “normal” range: REDs is not necessarily a clinically defined eating disorder from lecture by Professor J. Sundgot-Borgen (IOC working group on female athlete triad and IOC working group on body composition, health and performance).

No medical/physiological/metabolic parameter can be considered in isolation: in the case of REDs, it is not menstrual disturbance and bone health that are affected in isolation. For example, there is currently great debate about whether a low carbohydrate/high fat diet (ketogenic diet) can mobilise fat oxidation and potentially be a training strategy to enhance performance. Needless to say that a recent study contained no female athletes. Given that many female endurance athletes are already lean, potentially driving fat metabolism through diet manipulation may have an impact on Endocrine function, optimal health and hence sport performance. I understand that a forthcoming study will include female athletes.

So a continuum or distinct subgroups in the population? Clearly general medical principles apply to all, with a spectrum from optimal functioning, subclinical conditions through to recognised disease state. We now have evidence of distinct differences between subgroups in the population and even within these subgroups such as male and female athletes. We are moving into a world of personalised medicine, where recommendations for optimal health are tailored for individuals within specific subgroups.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance

References

How should we define health?

Nobody is average but what to do about it? The challenge of individualized disease prevention based on genomics

Exercise is Medicine

Enhancing Sport Performance: part 1

Keay N, Logobardi S, Ehrnborg C, Cittadini A, Rosen T, Healy ML, Dall R, Bassett E, Pentecost C, Powrie J, Boroujerdi M, Jorgensen JOL, Sacca L. Growth hormone (GH) effects on bone and collagen turnover in healthy adults and its potential as a marker of GH abuse in sport: a double blind, placebo controlled study. Journal of Endocrinology and Metabolism. 85 (4) 1505-1512. 2000.

Wallace J, Cuneo R, Keay N, Sonksen P. Responses of markers of bone and collagen turover to exercise, growth hormone (GH) administration and GH withdrawal in trained adult males. Journal of Endocrinology and Metabolism 2000. 85 (1): 124-33.

Wallace J, Cuneo R, Baxter R, Orskov H, Keay N, Sonksen P. Responses of the growth hormone (GH) and insulin-like factor axis to exercise,GH administration and GH withdrawal in trained adult males: a potential test for GH abuse in sport. Journal of Endocrinology and Metabolism 1999. 84 (10): 3591-601.

Keay N, Logobardi S, Ehrnborg C, Cittadini A, Rosen T, Healy ML, Dall R, Bassett E, Pentecost C, Powrie J, Boroujerdi M, Jorgensen JOL, Sacca L. Growth hormone (GH) effects on bone and collagen turnover in healthy adults and its potential usefulness as in the detection of GH abuse in sport: a double blind, placebo controlled study. Endocrine Society Conference 1999.

Wallace J, Cuneo R, Keay N. Bone markers and growth hormone abuse in athletes. Growth hormone and IGF Research, vol 8: 4: 348.

Cuneo R, Wallace J, Keay N. Use of bone markers to detect growth hormone abuse in sport. Proceedings of Annual Scientific Meeting, Endocrine Society of Australia. August 1998, vol 41, p55.

Subclinical hypothydroidism in athletes. Lecture by Dr Kristeien Boelaert at BASEM Spring Conference 2014 on the Fatigued Athlete

Optimal health: especially young athletes! Part 3 Consequences of Relative Energy Deficiency in sports Dr N.Keay, British Association Sport and exercise Medicine

Optimal health: including female athletes! Part 1 Bones Dr N. Keay, British Journal of Sport Medicine

Relative Energy Deficiency in sport (REDs) Lecture by Professor Jorum Sundgot-Borgen, BAEM Spring Conference 2015 on the Female Athlete

Effect of adaptive responses to heat exposure on exercise performance

Low Carbohydrate, High Fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers

Factors Impacting Bone Development

Optimal body mass index (BMI) coupled with favourable body composition of lean mass and visceral fat is associated with accrual of bone mineral density (BMD) and peak bone mass (PBM) which is vital for setting up BMD within normal ranges for adult life.

New research demonstrates that high BMI exerts a negative effect on the accumulation of BMD and bone architecture in young people. This is something of a surprise. Elevated BMI in young people is known to have a deleterious effect on cardio-metabolic health. However, to date the thinking has been that raised BMI would at least mean that weight bearing exercise would be “weighted” and hence favour accumulation of BMD. Rather it is reported that elevated BMI with increased visceral fat results in impaired bone architecture and BMD. Coupled with decreased lean mass, this means less muscle to exert force on the skeleton to promote BMD accumulation. This distorted body composition impairs attainment of PBM.screen-shot-2016-12-01-at-08-29-56

In my research, deficiency of BMD was found to be irreversible later in adult life, despite normalising body weight, shown for those at the other end of the spectrum of BMI. Those with relative energy deficiency in sports (REDs), formally known as the female athlete triad, demonstrated suboptimal BMD correlated with previous duration of low weight, amenorrhea and delayed onset of menarche, many years on despite return to optimal body weight and normal menstrual status.

Adverse body composition with increased deposition of visceral fat is seen in patients with growth hormone (GH) deficiency, for example post pituitary surgery. Interestingly in these young people with high levels of visceral fat, low levels of GH were recorded. The proposed mechanism of suppression of GH secretion in overweight young people has been discussed. Interestingly high levels of leptin are found in overweight youngsters, compared to low levels found my studies of low weight young dancers with menstrual disturbance. In other words, there appears to be feedback between body weight, body composition and the endocrine system. The other disadvantage of high levels of adipose tissue is that fat soluble vitamin D is “fat locked” and unable to support bone mineral accumulation.

Optimal BMI and body composition are factors associated with accrual of BMD and PBM which is vital for setting up BMD within normal ranges for adult life. In those young people with high BMI and disrupted body composition, dietary measures are needed to reduce body weight. Combined with exercise, including resistance and cardiovascular weight bearing forms, to improve body composition and thus bone architecture and BMD accrual.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance

References

Optimal health: including female athletes! Part 1 Bones Dr N. Keay, British Journal Sport Medicine

Optimal Health: Especially Young Athletes! Part 3 – Consequences of Relative Energy Deficiency in Sports Dr N. Keay, British Association Sport and Exercise Medicine

Science Daily

EurekaAlert

Paediatric Reports