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Sorcini et al., Rome, Italy, describe the incidence of birth defects
associated with congenital hypothyroidism (CH) in Italy between 1991-1996.
Out of 3,229,023 live births, 1029 infants with CH were detected (1:3128).
In 148 (14.4%) infants they found congenital abnormalities; 33/148 (22.3%)
showed more than 1 birth defect (BD). BD observed/expected (O/E) for the
central nervous system was 12, congenital heart disease 19.6, digestive
system 13.7, urogenital system 14, Down syndrome 6.7. Infants with CH and
BD had significantly lower values for serum T4, gestational
age, and birth weight when compared with CH only. (Comment: This interesting
study shows [again] that deficient thyroid hormone action in prenatal life
affects many systems of the body.)
It is still being debated if subclinical hypothyroidism, as defined by an elevated serum TSH but normal T4 and T3 serum parameters is an adequate compensatory mechanism ensuring euthyroidism to all tissues, or a state of less than normal thyroid hormone activity at the tissue level and should therefore be treated with thyroid hormone. Several reports were devoted to this entity, thus Caraccio et al., Pisa, Italy, reported further on their studies about muscle energy metabolism in 12 subclinically hypothyroid subjects with neuromuscular symptoms. In these subjects impaired muscle energy metabolism during dynamic arm exercise was detected in the sense that blood lactate was significantly higher during exercise, suggesting that muscle glycosis exceeds mitochondrial oxidation of pyruvate resulting in enhanced shunting of pyruvate to lactate via lactic dehydrogenase activity. After a six-months course of L-T4 treatment, lactate production completely normalized. (Comment: It should be asked if in patients with subclinical hypothyroidism but without neuromuscular symptoms, similar abnormalities are present.) Monzani et al., Pisa, Italy, evaluated the prevalence of neuromuscular symptoms in 33 consecutive patients with subclinical hypothyroidism and compared results with age and sex matched controls. Patients filled out a short questionnaire and those with 3 or more neuromuscular symptoms were then studied by electromyography (EMG). Significantly more neuromuscular symptoms were reported by patients versus controls. In 11/33 patients 3 or more symptoms were present and in 8/11 patients abnormal EMG findings (repetitive discharges) were detected. Upon T4 treatment a significant improvement of neuromuscular symptoms was observed, and EMG abnormalities disappeared. Furthermore, plasma total and ionized calcium was, be it in the normal range, significantly lower than in controls. PTH, phosphate and magnesium levels were normal. Calcium parameters normalized upon T4 replacement therapy. Tzotzas et al., Tessaloniki, Greece, compared results of thyroid hormone treatment on lipids and apolipoproteins profile in 24 patients with overt hypothyroidism and 23 patients with subclinical hypothyroidism. They found elevated levels of triglycerides, LDL, apoB, apolipoprotein B/A1 ratio and LP(a) levels before treatment in patients with overt hypothyroidism that decreased significantly after treatment. However, no abnormalities in these parameters were found before and during T4 treatment in patients with subclinical hypothyroidism. (Comment: Other published reports, however, show differences in lipid profile in subclinical hypothyroidism that normalize after thyroid hormone treatment ... the controversy continues.) |
