Pulmonary oxygen uptake kinetics during exercise in subclinical hypothyroidism

Area of Science:

• Exercise Physiology
• Endocrinology
• Cardiopulmonary Function

Background:

• Subclinical hypothyroidism (SCH) is associated with reduced exercise tolerance.
• The specific impact of SCH on oxygen uptake (VO2) kinetics during exercise remains unclear.

Purpose of the Study:

• To evaluate VO2 kinetics during and after constant-load submaximal exercise in women with SCH.
• To compare exercise response in SCH patients versus healthy controls.

Main Methods:

• 19 women with SCH and 19 controls (aged 20-55) underwent 6-minute constant-load (50W) ergospirometry and 6-minute recovery.
• VO2 kinetics were assessed using mean response time (MRT), oxygen deficit, and oxygen debt.
• TSH and free thyroxine (fT4) levels were measured.

Main Results:

• Patients with SCH exhibited significantly slower VO2 kinetics (longer MRT) during both exercise onset and recovery compared to controls.
• SCH patients demonstrated a higher oxygen deficit and oxygen debt, indicating greater reliance on anaerobic metabolism.
• VO2 kinetics showed a significant correlation with TSH levels.

Conclusions:

• Women with SCH display impaired VO2 kinetics during submaximal exercise transitions.
• This impairment suggests reduced aerobic capacity and is evident even in the early stages of SCH.