Osteoporosis in Athletes

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Osteoporosis in Athletes

Osteoporosis or osteopenia in athletes is associated with: the age of onset of training, duration,

intensity and volume of training, the sport concerned (e.g. light weight rowers, synchronised

swimmers, ballet dancers, gymnastics, marathon runners) diet and stress, psychological as well as

physical stress. The loss is mainly of trabecular bone, which is found in the vertebrae and the neck of thefemur.

Exercise plays a very important role both in the formation of bone and the maintenance of bone

throughout the life cycle. Bones require normal levels of sex hormones, adequate calories, particularly

protein. Daily Calcium 1000 -1500mg and 800 international units of Vitamin D and regular weight

bearing exercise. Exercise affects the skeleton in different ways. The direct effect of stress loading can

be to increase bone mineral density. Intensive aerobic exercise, however, can adversely affect bone

density indirectly by its effect on the hypothalamic-pituitary-gonadal axis, which results in low oestrogen

levels in females (Wolman 1994 ;O Brien 2007). Overtrained male athletes may also show low levels of

testosterone and may develop stress fractures and osteoporosis (Gillooly 2002, Rigby 2003).

Wolff's Law states that changes in bone function lead to changes in bone. Bone is laid down where it is

needed. Bone is resorbed where it is not needed (Wolff 1892). Osteogenesis is induced by dynamic not

static strains. The optimal type of osteogenic activity should provide relatively high levels of strain.

(Rubin and Lanyon1984). Tensile Forces result in osteoclastic activity on the convex side of an angulated

bone. Compressive force results in osteoblastic activity on the concave side.

Muscle action is the main stimulus for bone formation, the mechanical force and weight bearing. (O

Brien 2001). Greater loads and fewer repetition of a load will result in greater gains in bone mass. Lower

loads repeated a greater number of times result in lower gains (Kerr et al., 1994) Weight bearing activity

accounted for up to 17% of the variance in B.M.D. between individuals in their late twenties (Welten etal. 1994).

Peak Height Velocity for girls occurs usually between 10.5 - 13 Years and is earlier than 12.5 - 15 years

for boys. Around this period, bone is most responsive to exercise and during the time of Peak Weight

Velocity and Menarche, which occur approx 6 months and 1 year after Height Peak (Sanborn et al 1994).

Average age in Ireland is 12-13 years - A late menarche is after 16 years.

Bone mass is affected by peak bone mass and the degree of subsequent bone loss. 60-80% of Peak bone

mass is due to genetics. (Khan et al 2001) Other factors include, hormones, nutrition, environmental

factors and mechanical strain. Growing bone has a greater capacity to add new bone to skeleton than

mature bone, 7-8% gain of bone mass per year is gained during childhood and early adolescence.

(Matkovic et al 2000).

Many factors, hormones, diet, exercise, medication, and their chronological age, which can be affected

by their skeletal or bone age and the stage of sexual maturation, can affect Low Peak Bone Mass.

(McKay et al. 1998). Woods (1999) in a study of apprentice jockeys found that the majority had a bone

age 18-24 months below their chronological age. Apprentice jockeys had significantly lower BMD than


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flat and jump jockeys. The jockeys had lower BMD in spine and neck of femur than rugby players and

sedentary controls (Woods 1999).

Daily weight bearing exercise has a positive effect on BMD, while immobilisation and space flight have a

negative effect (Kanis 1994). The effects of exercise are not homogenous; they reflect the strains

imposed at individual sites. Osteogenic response to mechanical loading is site specific. ProfessionalTennis players have 30% greater bone density in dominant forearm (Krahl et al. 1994) Weight bearing

exercises such as running on the spot, jumping, skipping, dancing, walking are gravity stimulated and are

more effective than non weight bearing such as swimming, equestrian.

Weight bearing activity during adolescence and early adulthood was a far more important predictor of

peak bone mass than calcium intake. (Welten et al. 1994). Young women participating regularly in sports

at school demonstrated higher bone mass than those who did not. (Heinonen 2001).

Highest bone mineral content and bone mineral density are found in strength and power- trained

athletes. (Suominen 1993). World class and recreational weight lifters had 10-35% greater lumbar spine

B.M.D. Athletes with habitually high levels of physical activity show increased B.M.D. value when

compared with controls that undertake moderate physical activity. Road cyclists have lower bone

mineral density in their lumbar spine compared to mountain bikers. (Gillooly 2002, Rigby 2003).

Premenopausal women who participate regularly in high impact exercise tend to have higher B.M.D.

than sedentary controls. But intensive endurance training and amenorrhea may be associated with

decreased trabecular bone density in young females (Suominen 1993). Menstrual irregularities occurred

in elite university athletes, swimmers who had lower B.M.D. in their spine and hip than gymnasts.

Untreated amenorrhea is associated with long -term morbidity especially in young women (Drinkwater

et al 1990).

"Overtraining" due to excessive physical or psychological stress, particularly if it is associated with

inadequate caloric intake, results in low levels of sex hormones in both male and female athletes and an

increased risk of osteopenia or osteoporosis. There is a higher incidence of gonadal insufficiency

particularly in sports where there are weight categories, such as light weight rowing, judo, diving,

synchronised swimming, gymnasts, skating and ballet dancers, long distance running but it can occur in

any sport. Non-weight bearing sports particularly swimming and the lumbar spine in road cyclists are

prone to low bone mineral density, either osteopenia or osteoporosis. (Taafe et al. 1995).

Osteoporosis is a systemic skeletal disorder characterized by low bone mass and micro-architectural

deterioration of bone tissue, with a consequence increase in bone fragility. Osteoporosis is associated

with a reduction in bone mineral density and an increased risk of fractures. Bone is a dynamic tissue in

which the process of resorption, (mediated by the osteoclasts), is coupled with the processes of

formation, (mediated by the osteoblasts) when they are in a state of balance. Osteoporosis results when

uncoupling occurs and there is an imbalance between resorption and formation. The bone most

frequently affected is the trabecular bone in the distal end of the radius, vertebral bodies and the neck

of the femur. The commonest cause of osteoporosis in women and men is hypogonadism, which are

due to low levels of oestrogen in females and testosterone in males.


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Hormones secreted by the hypothalamus, anterior pituitary, and ovary and to a lesser extent the

adrenal gland regulate the menstrual cycle. Acting on the uterus and ovaries, they are dependent on a

feedback mechanism. This is necessary for the normal development of the follicle. The Gonadotrophin

Releasing Hormone (GnRH) causes the synthesis, storage, activation and release of Follicle Stimulating

Hormone (FSH) and Lutenizing Hormone (LH). The timing and intensity of the GnRH determines the

amount of FSH and LH released, and their ratio relative to each other. ( Prior 86 ). Physical exercise

produces marked changes in the post exercise pulsatile nature of LH, FSH and oestrodial. (Keizer 1983).

During strenuous exercise there is an increased concentration of dopamine, beta-endorphins and

Catechol-oestrogens. Dopamine has an inhibitory effect on the release of GnRH. Beta-endorphins act in

two ways; they appear to stimulate dopamine and this is their main action on GnRH (Yen, 1982), but

they also combine with the nor-adrenaline receptors in the hypothalamus and prevent the stimulatory

effects of nor-epinephrine on GnRH. The normal pulsatile release of gonadatrophin releasing hormone is

altered, resulting in changes in the secretion of FSH and LH and the ovarian hormones.

Corticotrophin - releasing hormone may also act indirectly by endorphins. The level of Cortisol is

increased by intense exercise and in athletes who are overtrained. Cortisol levels are increased in

amenorrheic athletes compared to sedentary women and cyclic athletes. Long term elevated levels of

Cortisol affect calcium and bone metabolism resulting in osteopenia and osteoporosis. Cortisol increases

bone resorption and decreases bone formation. Cortisol also decreases intestinal absorption of calcium.

Hypothyroidism may also be a complication of overtrained athletes who may also be amenorrheic.

Amenorrhoeic athletes who are hypo-oestrogenic have reduced bone mass. This may be due to late

menarche, irregular menstruation, or may be part of the Athletic Triad, which consists of amenorrhea,

an eating disorder and osteoporosis or osteopenia. (Khan et al 2001).

Menstrual irregularities result in alterations in the normal levels of sex hormones and predispose to

osteopenia and in some cases osteoporosis. Menstrual irregularities tend to occur in the athletes with

the most intense training schedules, who had trained for the longest period of time. Vegetarians and

people with a low caloric intake had the highest incidence of oligomenorrhea and amenorrhea.

Menstrual irregularities are not consistent across sports; 7% recreational runners, 12% swimmers and

25% distance runners. Many so-called normal cycles are abnormal when serum hormone levels are done

after 21st day of cycle.

There are multifactorial causes; Stress, both psychological and physical stress. This may be due to an

increase in the amount and intensity of training and in the numbers of competitions with inadequate

rest periods.

Other factors which predispose to menstrual irregularities include a late menarche (>16 years), irregular

cycles prior to sports participation, intense training prior to menarche, immature pituitary axis. Tall thin

girls and those with a poor maternal menstrual history, have a later menarche than small overweight

girls. Average age for menarche in USA for Caucasians is 12.8 years, for European's it is 12-13.4 years.

Progression of menstrual changes to abnormal is from,


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1. Normal follicular, phase and a normal luteal phase.2. A prolonged follicular phase and a shortened luteal phase, this can only be diagnosed by taking

bloods to measure progesterone levels after the 21st day of the cycle. Luteal phase defects are

associated with low progesterone levels, premenstrual tension and infertility.

3. Further progression results in euoestrogenic anovulatory oligomenorhea, if this phase persiststhere is a risk of endometrial hyperplasia.

4. Hypo oestrogenic amenorrhea results in osteoporosis and genital atrophy due to low levels ofoestrogen. (O'Brien 2007 , Shangold 1988).

Diet also plays an important role. Decreased caloric intake and a high fibre diet are associated with a

raised level of Serum Sex Hormone Binding Globulin and lowered levels of biological active oestrogens.

There is a higher incidence of amenorrhea in athletes who have a low caloric intake or who are

vegetarians. The increased fibre is thought to bind with calcium and reduce calcium absorption. Excess

fibre may also lead to decreased bone density by the binding of steroids to fibre or indirectly by

decreasing enterohepatic circulation of oestrogens, either of which would have a negative effect on

bone remodelling.

Increases in dietary fat consumption are associated with increased levels of circulating oestrogens.

Amenorrheic athletes have an increased risk of musculosketal injuries and may have a low calcium and

vitamin D intake. The recommended daily calcium for an adolescent is 1500mg and 800 international

units of vitamin D.

Drinkwater et al (1990) reported vertebral BMD to be significantly lower in athletes with a long history

of menstrual irregularity. There is a higher incidence of stress fractures in amenorrheic athletesparticularly those with a late menarche. (Warren et al. 1991). The mean bone mineral density is

comparable in some cases to a 60-year-old woman. If untreated they have a high risk of developing

stress fractures now and osteoporotic fractures now and also at the menopause. Moderate exercise

protects but excessive exercise may cause osteoporosis.

"The Athletic Triad" (Yeager et al 1993) is the name of the syndrome, which occurs, in female athletes,

when amenorrhoea, an eating disorder and osteoporosis occur together. Bennell 2004: Khan et al. 2004

have found that they may have osteopenia rather than osteoporosis. They may each occur on their own,

or in combination.

The female athlete is most at risk to develop the athletic triad during adolescence and young adulthood.

This may be due to psychological, biological and social pressures at this time. During the prepubertal

spurt 60% of the final bone mass is laid down. Anorexia and bulimia are now more frequently

recognised, both in the general population and among athletes (Grinspoon et al., 1999; Sundgot-Borgen,

1993; Sundgot-Borgen, 2000; Miller et al., 2005).


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Individuals with eating disorders strive for perfection; have a marked preoccupation with food, a

distorted body image and fear of gaining weight or becoming fat, despite being at least 15% below their

ideal body mass. Amenorrhea is one of the cardinal features of anorexia and is associated with

hypothalamic dysfunction with low levels of oestrogen (Lindsay 1995; Compston et al., 2006); in

addition, anorexics may also have high levels of the stress hormone cortisol (Katz, 1988). BMD is also

significantly lower in females who have developed anorexia during their growth period than in those

who have developed anorexia at an older age (Biller et al., 1989).

Athletes, parents and coaches, who have unrealistic goals and poorly designed training programmes

with inadequate recovery periods are placing the athlete at a much higher risk of developing an eating

disorder. Talented athletes participating in more than one sport and who are training and playing for

school club and county, "Win at all costs, ambitious coaches, and pushy parents with unrealistic goals,

wrong training plan, emphasis on weight," are detrimental to talented athletes.

Osteoporosis in young female athletes is sports specific; there is a much greater incidence in appearance

sports, such as diving, figure skating, gymnastics synchronised swimming and ballet. Endurance sports,

which involve distance running, particularly in marathon runners. Weight category sports: jockeys, judo

and light weight rowers. It is associated with age of onset of training, duration of participation in

training, intensity and volume of training, the sport concerned, diet and stress (Riggs, 1981).

Stress, both psychological and physical , play a role in menstrual irregularity, which may progress to

oligomenorrhea or amenorrhea. Physical stress may be due to a sudden increase in the intensity and

duration of training or too many competitions. A sudden marked increase in the intensity and the

amount of aerobic exercise may cause problems particularly in the younger nulliparous female with an

immature hypothalamic - pituitary axis.

Nattiv et al. (1994) state that eating disorders such as anorexia and bulimia affect as many as one thirdof athletic females. Disordered eating has become a major concern in female and in some male athletes.

Some researchers have estimated the prevalence to be as high as 50% in certain sports. Female athletes

who had a late menarche (after 16 years) or who have irregular cycles, particularly if they have had long

periods of oligomenorrhea or amenorrhea, e.g. athletes with eating disorders and hypogonadism due to

any cause, are more at risk to develop osteopenia or osteoporosis, particularly if they are " overtrained".

Long-term Corticosteroid users, patients with malabsorption, hypothyroidism, and hyperparathyroidism,

high levels of prolactin, Cortisol, Parathyroid hormone, hyperthyroidism, low levels of vitamin D are also

at risk.

If a female athlete has been amenorrhoea for six months and is not pregnant, hormonal studies shouldbe carried out and her bone mineral density should be assessed using a Dual Energy X-ray

Absorptiometer (DXA). DXA is non invasive and is currently the most precise and widely used method of

assessing Bone Mineral Density. Measurement of the spine and hip should be carried out and bone

markers, if they are available. If osteoporosis is diagnosed in either a male or female she/he should be

treated. Medical causes must be excluded.

The treatment for amenorrhoeic athletes:


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1. Reduce the amount and intensity of the exercise and competition.2. Reduce psychological stress if possible.3. Prescribe combination low dose pill or HRT.4. Increase the calcium content to 1000-1500mg per day.5. Increase the total calorific content, if it is below the required level for the activity performed.

They should be advised to decrease their exercise intensity and a 2-3% increase in weight should be

encouraged. Recreational athletes will reduce the intensity of their exercise; elite athletes are unlikely to

take this advice. If the female athlete will not reduce the amount of training and competition, she

should be advised to go on hormone replacement therapy or the low dose contraceptive pill. Some

athletes do not want to go on any medication, as they think it will affect their weight, but they must

consider that if they get a stress fracture they will be unable to compete or train.

All athletes should keep a training diary, which should include details of their diet, exercise regime and

menstrual cycle. Excessive carbohydrate loading may result in some athletes developing diarrhoea, due

to intolerance to gluten. This will affect absorption of Calcium, vitamin D iron and protein.

"Overtrained athletes" you should measure sex hormones, oestrogen, progesterone, serum sex

hormone binding globulin (SHBG),and free testosterone, androstenedione in males, cortisol,

gonadotrophins (LH,FSH ) and prolactin, thyroid, hepatic, and renal and intestinal function. Female

athletes who had a late menarche, or irregular cycles, particularly if they have had long periods of

oligomenorrhea or amenorrhea are more vulnerable and should have a DXA and hormone levels done in

the second half of the cycle if they are having periods.

Maximum bone loss probably occurs in the early phase of amenorrhoea, so they should start treatment

early. A large number of amenorrhea athletes develop breast tenderness and bloating, when they start

hormone therapy and they should be warned about this and reassured that the symptoms are usually

transitory. Adolescent athletes are at high risk of developing eating disorders.

All athletes should be given nutritional advice from a nutritionist interested in sport and eating disorders

and consult a psychiatrist with a special interest in eating disorders. Ensure they have an adequate

caloric intake and increase the calcium intake to 1500 mg, and 800 IU of vitamin D.

Medical Team Approach: Physician, Physiotherapist, Nutritionist, Physiologist, Psychologist working with

athlete and coach. The successful treatment and prevention of Osteoporosis is to identify those at risk atan early stage and assess their hormone levels and bone mineral density.

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Professor Moira O Brien FFSEM

Osteoporosis in Athletes

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