A woman, 76 years old, was admitted to our hospital for fatigability, puffy face and leg edema in August, 1992. In 1985, she had suffered from a right thyroid tumor. The data of thyroid function tests are shown in Table 1. The 99mTc and 123I thyroid scintigraphy indicated large functioning thyroid nodule in right thyroid lobe [123I uptake: 37.6% (3h), 40.6% (6h) (normal range 6h. 8-25%)] with suppresstion of left lobe. In the following year, she got an operation of the thyroid gland for functioning follicular adenoma of the right lobe and nodular hyperplasia (adenomatous goiter) of the left one. The right lobe of the thyroid had been totally resected and only half of the left lobe remamed. Before and after the operation, free T4 and TSH levels were below normal range and desiccated thyroid was administered. The thyroid evaluation, performed after three months following the operation, was hypothyroid state as follows; T3 (66ng/dl), T4 (5.3mug/dl), F-T4 (0.29mug/dl) and TSH (32.3 muU/ml) (Table 1). The dosage of desiccated thyroid was increased to 60mg and serum TSH level became low level. In May, 1991, thyroid function test showed normal serum total thyroid hormone, suppressed TSH and low free T4 levels. Thereafter her compliance of taking drugs was insufficient.
On admission, (in August, 1992), she appeared clinically to be myxoedematous because of puffy face and non-pitting leg edema. On physical examination, the body temperature was 36.5 C, pulse rate 72 beats per minute and regular, and blood pressure 132/70mmHg. The hair and skin were normal. Thyroid gland which remained was not palpable.
Urinalysis, hemogram, levels of electrolytes, blood urea nitrogen, blood glucose, uric acid, cholesterol and liver function were within normal limits. The roentogram of the chest revealed an enlarged heart. Electrocardiogram showed left ventricular hypertrophy. To evaluate the pituitary-thyroid function, the administration of desiccated thyroid was discontinued for one week after this admission. TSH was still suppressed despite low level of T4 (1.6mug/dl), T3(15ng/dl), free T4(0.15ng/dl) and free T3 (below 0.4). Serum TBG level was 20.5mug/ml and anti-thyroglobulin, microsome antibodies, TSH receptor antibody and anti-TSH antibody were negative. As shown in Table 2, a significant increase in serum TSH levels did not occur after drip infusion (2mg) of TRH for 30 minutes. After repeated injection of TRH (2mg/day) for 4 consecutive days, serum TSH levels were still suppressed (maximum level: 1.45muU/ml in 120 minutes of final injection day). With the final TRH injection, combined pituitary stimulation test by intravenous injection of 0.1 units/kg reglar insulin, 0.1mg LH-RH was performed. Growth hormone (GH), LH, FSH, prolactin (PRL) and cortisol kept almost normal responses (Table 2). The pituitary MRI and CT did not show any abnormality. These results were consistent with secondary hypothyroidism derived from the isolated deficiency of TSH.