I don't know how many parts this theme will have. Today we'll talk about the complex and still controversial association between activity/inactivity levels and thyroid response.
Lower than what? Lower than the controls in that experiment. The measured parameters were:
  • - Handgrip and quadriceps muscle strength (assessed by  dynamometer)
  • - Functional exercise capacity (assessed by 6-minute walk test (6MWT))
This is not a "duh" claim. The number of factors, endocrine, and neural networks involved in metabolism regulation is so complex that any "duh" reaction reflects a "duh" mind. It's not simple. It's not obvious. It's damn serious.
We are seeing it every day. Folks that don't have a chance to get a minimum level of physical activity have a higher chance of manifesting thyroid problems. Thyroid problems reflect on almost everything: from depression to digestion, from dyslipidemia to reproductive issues.
Stress makes it all worse: "The stress response was higher in isolated males than females, but in males, it did not alter the effects of exercise, in contrast to isolated females that had a blunted response to exercise compared to controls. In conclusion, chronic stress interferes with metabolic effects produced by exercise, such as loss of WAT mass, coincident with dampening of HPT activity".
Chronic exercise is associated with healthiER levels of thyroid function and even elite-level chronic exercise, which produces paradoxical thyroid responses, is not associated with hypothyroidism except in certain conditions.
The key here seems to be how to figure out what is the optimal and the minimal chronic exercise level, type, and frequency to maintain thyroid function. Nobody knows. It is mostly associated with cardiovascular exercise but how much and how frequently high-intensity interval training (HIIT) or steady-state endurance exercise (SEE) is also individually contextualized.
The bottom line is that thyroid dysfunction during periods of physical activity change (more or less, with calorie deficit or superavit, and we'll leave that for later) requires analyzing physical activity patterns. More than that, it requires analyzing longitudinal physical activity patterns.
Unfortunately, that's not something the immense majority of physicians are equipped to do.
What can YOU do about it?
  • ONE - "If it ain't broke, don't fix it". Pay attention to your patterns. If you are healthy, pay even more attention. Life is dynamic. Chances are high that you will face disruptions.
  • TWO - take inventory of your physical activity levels going back at least 10 years. You will probably see that there are significant changes in activity patterns and "stuff" happening at the same time. Sometimes you are physically inactive because of a serious infection and you will lose weight. Sometimes you will be inactive for other reasons and you will gain weight, lose hair, become depressed, have brain fog and blurred vision.
Figure it out.