FIRST PUBLISHED IN ISSUE 104 (2012)

 

As physicians and endocrinologists, we are used to seeing people with life-threatening endocrine disorders, and to helping people manage the frequently disabling consequences of chronic conditions. However, there are those who have a chronic endocrine disorder, but are at the peak of physical fitness. These unusual individuals require specific support, and we have developed a service to help them manage their endocrine and other disorders and also excel in sports.

MY ARRIVAL IN THE ARENA
My interest in this field was accidental. I had studied the physiology of energy expenditure for my MD, and am a keen, but now failing, rower. In 1997, Steven Redgrave came to see me to discuss his then newly diagnosed diabetes. Steven was preparing for his fifth Olympic Games, this time rowing in the ‘coxless fours’ event. Steven was sceptical but pleased to hear that I believed that, with careful management, he could return to maximal physical performance, and be able to compete at the 2000 Olympic Games. I believed that this might be possible because Steven had extensive pre-diabetes physiological studies which would provide a unique baseline to work from, and because short-acting analogue insulin had recently been introduced.

TEETHING PROBLEMS
The initial period of conventional diabetic management was a failure, with Steven complaining of very low levels of energy and work output, and suffering frequent episodes of hypoglycaemia on the water. We decided to return Steven to his successful pre-diagnosis food intake and training programme, and to manage his diabetes around the 6,500–7,000 calorie diet of high glycaemic index foods. This would require the development of an unusual multiple daily insulin injection regime. To maintain glycaemic control avoiding hypoglycaemia required five or six injections of analogue insulin per day, each at a very small dose, and two unusually timed basal insulin doses.

Initial progress was swift, but further issues were identified following high energy expenditure rowing events. Again, physiological studies were essential to identify problems with refeeding and energy storage. Further refinement of this regime enabled specific refeeding programmes to normalise Steven’s work output to close to that seen before diagnosis of diabetes.¹

FINE TUNING
In the preparation for the Olympic Games, every potential rowing eventuality, such as delayed start of racing, repechage (additional races for qualification) or multiple races in a day, was considered and the appropriate response practised. The iconic video image of the race and Steven’s celebrations has been voted as our outstanding sporting achievement.

As a result of the publicity following Steven’s success, young sportsmen with diabetes asked to see us to help in their management. Over the following decade, we have found that patients attending the service complain of three main groups of symptoms:

• seemingly inexplicable dysglycaemia during and immediately following exercise
• unexpected and severe hypoglycaemia, particularly at night
• excessive fatigue, impaired physical performance and increased muscle weakness and cramps when compared with their prediabetic state or with peers (this is probably the most subtle of the three groups of symptoms).

To deal with these issues, we aim to reduce day-to-day variation in insulin therapy technique and to improve insulin dosage relative to carbohydrate intake. A focus on detail is extremely important, as we frequently find that much of the apparently inexplicable variation in glycaemic control is not due to exercise but due to these factors. A detailed history of the sporting/exercise programme is made. Particular attention is paid to the timing, duration, intensity and type of exercise on each day of the week. This allows the exercise to be characterised so that the anticipated effect on blood glucose levels can be identified. In general, the exercise is classified as endurance (in which case blood glucose can be predicted to fall), high intensity (where blood glucose is likely to rise) or mixed exercise, such as team sports, where the effect may be variable from day to day, depending on the intensity of each event (although the general effect tends to be a fall in blood glucose levels which is attenuated when compared with pure endurance exercise).

Importantly, the timing of each event in relation to the bolus dose of insulin is identified, as well as any adjustments which are made to this dose. Particular care and attention are paid to symptoms suggestive of hypoglycaemic unawareness. Severe hypoglycaemia in young adults who are sleeping on their own is of special concern, and where found requires specific attention. Listening to what those young people had to tell us has led to practical recommendations for managing different sporting activities.² The experience of our patients is also disseminated though our website (www.runsweet.com) and its forum.

ACADEMIC PERSPECTIVE
There was, however, a significant lack of scientific evidence underlying this clinical field. Steven Redgrave’s experience spurred on our investigations and those of others in this area, and we now have good evidence of the metabolic and endocrine effects of insulin-treated diabetes on risks and avoidance of hypoglycaemia, and on how to optimise insulin and continuous insulin infusion therapy.^3,4

We understand the hormonal and metabolic responses to exercise, how these responses are altered by type 1 diabetes and insulin therapy, and how a number of endocrine disturbances can influence glucose regulation during exercise, making the management of glycaemia challenging for patient and caregiver. We have seen how increased insulin sensitivity and the reduction in counter regulatory hormone response to hypoglycaemia seen following exercise, particularly in men, may predispose to severe nocturnal hypoglycaemia. There remains a lot more to understand.

Our particular interest is managing perceived impairment in physical performance in diabetes, but we have been asked to review athletes without diabetes, who have performed well, but who are currently off the pace. Such impairment of performance is frequently attributed to a ‘post-viral’ condition. This has lead to a further, very interesting area of development. We are able to study these young people in our well equipped exercise laboratory and, following a standardised exercise programme to exhaustion, we can monitor gas exchange, electrolytes and intermediary fuels. In the cases we have studied, we have found interesting variation of glucose metabolism, alteration in fuel utilisation and variation in electrolyte fluxes at maximum performance which have responded to treatment.

THE FUTURE
The merging of endocrinology, physiology and metabolism provides a fascinating clinical experience and an exciting new area for translational clinical research. For the athletes, it offers the promise of a return to optimal performance. The prospect of the Olympics coming to London provides a good springboard for the UK to be at the forefront of this area.

IAN GALLEN

REFERENCES
1. Gallen IW et al. 2003.Clinical Medicine 3 335–337.
2. Nagi D & Gallen IW 2010. Practical Diabetes International 27 158–163a.
3. Lumb A & Gallen IW 2009. Current Opinion in Endocrinology, Diabetes & Obesity 16 150–155.
4. Gallen IW (Ed.) 2012 Type 1 Diabetes: Clinical Management of the Athlete. London: Springer-Verlag.