PMC6107079_01
PMC6107079_02
New resistance to thyroid hormone kindred harboring A317T mutation in TRbeta
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F1
Family history was remarkable for mother who had died at age 88 years and suffered with hyperthyroidism and atrial fibrillation, an identical twin sister previously diagnosed with RTH (case 2; figure 1), three adult children (ages 41, 33 and 28 years old) alive and in good health, and five grandchildren (ranging in age from 7-14 years old) who were all reportedly asymptomatic (figure 1), i.e. no hyperthyroidism, goiter or cardiac ailment.
Effect of L-T3 suppression (25 micrograms daily) on TSH and free T4 level. Serum thyroid stimulating hormone (TSH), and free thyroxine (T4) were determined at the five indicated time points on the x-axis during a 319 day observation period. Cytomel (L-T3), 25 micrograms was prescribed to be taken once daily in the morning during a three week period starting on day T+150 (ON) and ending on day T+171 days (OFF), All TSH and free T4 levels were performed using the same laboratory assay except for the day 1 TSH level which had a slightly higher upper limit of normal value, i.e. 5.2 uIU/mL compared to the remaining TSH values (upper limit, 4.5 uIU/mL).
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F2
After three weeks' L-T3 treatment, repeat thyroid function tests demonstrated a 22% decline in the free T4 level, unchanged total T3 level and a 50% decline in TSH level compared to basal levels (T+171 vs T+115 days; Table 1; Figure 2). After discontinuation of L-T3, however, free T4 and TSH levels reverted to their pre-treatment levels (T+ 201 days; Table 1; Figure 2), and dizziness and dyspnea also recurred requiring the patient to be hospitalized again and treated for congestive heart failure.
PMC6107079_03
Longitudinal change in left atrial size in 59 year old woman (case 1) harboring heterozygous A317T mutation in TRbeta gene. Left atrial size was determined by serial echocardiography performed approximately three years apart, i.e. ~T- 975 days (2015) and T+ 120 days (2018). The lower and upper limit of the normal range for age-matched adult women (2.8-4.0 cm) is indicated by the dashed lines.
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F3
During previous hospital admissions for congestive heart failure the patient (Case 1) had undergone repeated two-dimensional echocardiography which showed a progressive increase in left atrial size from 3.3 cm to 4 cm over a three-year observational period (Figure 3).