Hypothyroidism is defined as a clinical state resulting from insufficient
secretion of thyroid hormone from thyroid gland due to some structural or
functional impairment of thyroid hormone production. Hypothyroidism affects
several organs systems. Clinical symptoms of hypothyroidism include fatigue,
depression, weakness, modest weight gain, cold intolerance, disturbed sleep,
dry coarse hair, constipation, dry skin, muscle cramps, poor concentration, less
memory, irregular and inconsistent menstrual cycle etc. All such signs and
symptoms are recovered after replacement of thyroid hormone (Larsen, 2003).
Studies have shown that both myxoedema and hypothyroid state produce
depression of hypoxic ventilator drive which is responsive to replacement
therapy. This alteration in ventilator control may contribute to the
hypoventilation seen in myxoedema and hypothyroidism (Zwillich, 1975).
Hypothyroidism affects respiratory muscle strength which is linearly related to
the thyroid hormone levels. Muscular weakness is present in both inspiratory
and expiratory muscles and is reversible with treatment (Siafakas, 1972).
Studies have shown that sleep pane episodes are common in person with
untreated hypothyroidism even with normal lung function. Thyroxin
replacement therapy decreases apnea frequency, even without change in body
weight (Larsen, 2003).
