The thyroid and parathyroid glands are anatomically situated in the front part of the neck, but have different functions.
The thyroid is a butterfly-shaped gland near the voice box, which helps regulate the body’s metabolism.
The parathyroid is attached to the back of the thyroid gland and produces parathyroid hormone that helps regulate calcium, phosphorus, and vitamin D levels in the bone and blood (Vanders Human Physiology, 2008).
Abnormalities in either of these glands can result in a cascade of metabolic issues, which can negatively affect health status.
Conditions affecting the thyroid gland include:
- Hypothyroidism (low thyroid hormone): may result in weight gain, fatigue, and depression.
- Hyperthyroidism (high levels of thyroid hormone): may cause weight loss, nervousness, and a rapid heart rate.
- Hyperparathyroidism results in the secretion of high levels of parathyroid hormone which may cause high calcium levels and other non-specific symptoms such as weakness, fatigue, depression, or aches and pains (National Endocrine and Metabolic Diseases Information Service).
Rationale for Exercise with Thyroid and Parathyroid Disease
There is very limited scientific research surrounding the impact of exercise training on thyroid function and specific exercise guidelines have yet to be established.
Studies in healthy, well-trained male athletes have shown that high intensity exercise can increase (Ciloglu et al 2005) or decrease (Hackney & Dobridge 2009) levels of circulating thyroid hormones. Though these reports offer conflicting results, it is important to remember that these findings may not apply to individuals with diagnosed thyroid dysfunction who may suffer from other health conditions that might influence hormone levels.
There is also limited evidence surrounding the impact of exercise on parathyroid function. Two earlier studies showed that a single bout of aerobic exercise in apparently healthy women (Thorsen et al 1997) and long-term moderate endurance exercise in men (Ljunghall et al 1986) resulted in increased levels of parathyroid hormone up to 72 hours after exercise.
Hyperparathyroidism results in increased levels of circulating parathyroid hormone and exercise may induce an additive effect on this hormone that may further raise calcium levels and impact upon bone metabolism.
Bouts of tachycardia (abnormally elevated heart rate) have also been observed in hyperparathyroidism (Chang et al, 2000), so clearly this condition must be medically managed prior to engaging in structured exercise.
Exercise Prescription for Thyroid and Hyperthyroid Disease
More research is required to determine the effects of exercise on individuals with thyroid and parathyroid dysfunction. As a general rule, you should first ensure that your condition is well-managed and under the care of a qualified medical practitioner (i.e. endocrinologist) before participating in exercise.
Thyroid disorder exercise guidelines
- Frequency: ≥ 5 days per week to maximise energy expenditure (if obese) and/or improve cardiorespiratory fitness where weight control is not a primary concern.
- Intensity: 40 to 75% heart rate reserve. Progress to higher intensities as tolerated, notwithstanding any precaution advised by your doctor.
- Time (Duration): 30 to 60 minutes per day. If you are unable to tolerate long, continuous activities, consider intermittent bouts of 10 minutes duration accumulated throughout the day.
- Type: Select aerobic exercises, which engage the large musculature of the body. Perform resistance-training and progress as tolerated (ACSM)
Resistance Training and Thyroid Disease
The guidelines for resistance training in people with diagnosed and medically-managed thyroid and parathyroid dysfunction may be similar to those of the apparently healthy population. However, you should be prepared to adjust exercises as necessary to address specific other health problems and/or physical limitations:
- Frequency: Resistance training for each major muscle group 2 to 3 days per week with at least 48 hours separating the training sessions for the same muscle group.
- Intensity (sets and repetitions): Train each muscle group for a total of 2 to 4 sets with a range of 8 to 12 repetitions per set with a rest interval of 2 to 3 minutes.
- Duration: Session duration will vary depending on the number of exercises performed.
- Type: Adults are recommended to perform multi-joint exercises affecting more than one muscle group and targeting opposing (agonist/antagonist) muscle groups. Single joint (isolation) movements may also be performed, but remember to consider the planes of movement and try to incorporate functional exercises with relevance to your activities of daily living.
Exercise may play a therapeutic role in the treatment of thyroid and parathyroid disease, though medication and/or surgical intervention may be the preferred first line of treatment in hypo/hyperthyroidism and hyperparathyroidism, respectively.
Conditions that affect exercise capacity
- Low energy levels: radioactive iodine or anti-thyroid medications such as methimazole or propylthiouracil are common treatments for hyperthyroidism and may leave you feeling lethargic. In the case of hypothyroidism, even if medicated, you may also experience early onset fatigue. Pay attention for changes in your energy levels, as this may warrant a reduction in exercise workload or resistance.
- Blunted heart rate response: Hyperthyroidism may be treated with beta-blocker medications, which can blunt the heart rate response. Therefore, heart rate may not be an accurate indicator of the exercise intensity and rating of perceived exertion may be a sufficient alternative.
- Obesity and weight gain: If you have hypothyroidism in the setting of obesity, work towards weight loss and enhanced energy levels. Treatment for hyperthyroidism may plausibly lead to a reduction in energy expenditure and weight gain. It may be necessary to make modifications in exercise frequency, intensity, duration, or modality to accommodate your level of deconditioning or larger body frame (if obese).
- Cardiac considerations: Levothyroxine is commonly prescribed for hypothyroidism and may cause tachycardia, palpitations, arrhythmias, and increased blood pressure. Exercise causes an expected rise in heart rate and blood pressure and the medication may exacerbate the response. You should diligently monitor both of these parameters before, during, and after exercise and report all adverse events to your doctor.
- Other health conditions: Thyroid dysfunction may present in the setting of other comorbid conditions such as diabetes, hypertension, or altered blood lipids. You may need to monitor additional parameters (i.e., blood sugar, blood pressure, or side effects to dyslipidaemia medications).
- Bone and joint pain: Hyperparathyroidism may promote bone loss due to its effects on calcium status. Once treatment has been initiated for this condition, weight bearing exercise may help stimulate bone growth and strength. Monitor for signs and symptoms of discomfort in the bones or joints, which may be residual effects from the condition.
- Weakness and compromised balance: Pay attention to the possibility of compromised balance if you’ve experienced significant bone loss and fatigue.
- Calcium levels: Hyperparathyroidism essentially starves the bones of calcium. Though surgical treatment of the parathyroid gland should improve this condition, in some cases, it may result in chronic low calcium levels. It is advisable to work in partnership with your doctor in monitoring calcium and vitamin D levels and the extent to which these levels may impact upon your exercise capacity (particularly resistance training).
- Comorbidities: As with thyroid disease, you should apprise yourself of any other accompanying health conditions or medications, which may impact your ability to perform exercise.