In 8 patients (3 men and 5 women) with short-term primary hypothyroidism before and during replacement therapy, and in an age-matched control group (9 men and 7 women), we assessed maximal inspiratory muscle force (Pimax) and the ventilatory control system at neural (EMG), muscular (P0.1), and ventilatory (VE and Vt/Ti) levels. While hypothyroid, patients exhibited a significantly lower Pimax. During a CO2 rebreathing test, hypothyroid patients exhibited similar diaphragmatic electromyographic (EMGd) and ventilatory (VE) response slopes to increasing end-tidal CO2 tension (ΔEMGd/ΔPetCO2 and ΔVE/ΔPetCO2), but significantly less ΔP0.1/ΔPetCO2 (p2 (p3), Pimax (p0.1/ΔPetCO2, and Δ(Vt/Ti)/ΔPetCO2 response slopes were found to be significantly increased (p3 increases both force (P0.1 and Pimax) and velocity (Vt/Ti) of inspiratory muscle contraction.
- Breathing control
- L-triiodothyronine replacement therapy
- Mouth occlusion pressure
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine