Relation Between Thyroid Hormone Stimulated Mitochondrial Function and Spontaneous Abortion and Complications of Pregnancy in Subclinical Hypothyroidism

The aim is to estimate the relationship between SH and spontaneous abortion and/or obstetric complications because of mitochondrial dysfunction.

1. A prospective study where data from the General Suburban Population Study in Naestved will be analyzed to measure the frequency of subclinical hypothyroidism (SH) and TPOab. SH is defined as raised serum concentrations of TSH > 3,4 mU/l and normal levels of free T4 and T3. A cut-off of 60 mU/l is used for TPOab.
2. To estimate the relationship between SH or TPOab and early spontaneous abortion and pregnancy outcome. Inclusion of women who have experienced a minimum of one early spontaneous abortion and between 20 and 50 years old: 50 women who have SU and/or TPOab-positive and 50 women who have normal levels of TSH and TPOab-negative. The basal oxygen consumption will be measured and mitochondrial functions will be determined by flow cytometry.
3. To estimate the prevalence of gestational hypertension and pre-eclampsia among pregnant women with subclinical hypothyroidism and estimate the mitochondrial function. A minimum of 100 pregnant women without any thyroid disease or diabetes will be included.

Early spontaneous abortion is defined as abortion before 12 weeks of gestation. Obstetrics complications are defined as pre-eclampsia (proteinuria, oedema, hypertension), pregnancy-induced hypertension, placental insufficience (IUGR) and abruption, preterm delivery and stillbirth. Those complications will be analyzed from the data of the obstetric journals.

Measurement of oxygen consumption:

Respiratory gas analysis and volume measurements were performed with a canopy connected by a triple V (flow⁄gas sensor) to an Oxycon apparatus (Jaeger Oxycon Champion, Breda, the Netherlands). The equipment was calibrated before each test to compensate for ambient conditions such as air pressure, temperature and humidity. Basal VO2 was measured after at least 6 hours fasting. Before the test the individual resting pulse was established and the participants rested for about 30 min in a chair. The test room was quiet and the lighting was subdued. The subjects were given sufficient time to become familiarized with the equipment and the procedures and the test was initiated when the resting pulse was achieved. Oxygen consumption was measured when the uptake per minute remained constant. Measurements were performed for repeated periods of 30 seconds for 20 minutes. The method for recording oxygen uptake had a within-day variation of 0.8 % and a day-to-day variation of 5.8 %.