Persistent pituitary resistance to thyroid hormone in congenital versus later-onset hypothyroidism.
The pituitary and peripheral responses to L-T4 and L-T3 therapy were studied in 12 patients with congenital goitrous hypothyroidism, in 10 patients with an ectopic thyroid and onset of hypothyroidism at 3-8 years of age, and in 6 patients with adult-onset hypothyroidism, after they had had their chronic thyroid hormone replacement therapy discontinued for 30 days. They were first treated with increasing L-T4 (0.1, 0.2 and 0.4 mg daily) followed by L-T3 (0.05 and 0.2 mg daily) after stopping thyroid medication for another month. Ten normal subjects were treated identically. In normal individuals the peak TSH, alpha, and TSH-beta response to TRH was significantly decreased with 0.1 mg L-T4 or 0.05 mg L-T3 daily and was suppressed with 0.2 and 0.4 mg L-T4 or 0.2 mg L-T3 daily; serum cholesterol and triglyceride decreased significantly with 0.2 or 0.4 mg L-T4 or 0.2 mg L-T3 daily; testosterone-estradiol binding globulin (TeBG) increased significantly at the same doses. In congenitally hypothyroid patients receiving 0.2 mg L-T4 daily, the mean peak TSH after TRH was 24 +/- 17 microU/ml, whereas in patients with an ectopic thyroid or adult-onset hypothyroidism the peak TSH was significantly less at 5.9 +/- 8.8 and 5.5 +/- 5.7 microU/ml, respectively. Only at the highest doses of L-T4 (0.4 mg/day) or L-T3 (0.2 mg/day) was the TSH response to TRH suppressed in the congenitally hypothyroid group. The alpha and TSH-beta subunit levels followed those of TSH.(ABSTRACT TRUNCATED AT 250 WORDS)
D000293:Adolescent; D000328:Adult; D002648:Child; D002784:Cholesterol / Q000097:blood; D003409:Congenital Hypothyroidism; D004351:Drug Resistance; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy*; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects*; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013963:Thyroid Hormones / Q000627:therapeutic use*; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone; D013974:Thyroxine / Q000627:therapeutic use; D014280:Triglycerides / Q000097:blood; D014284:Triiodothyronine / Q000627:therapeutic use
D012738:Sex Hormone-Binding Globulin; D013963:Thyroid Hormones; D014280:Triglycerides; D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D002784:Cholesterol; D013974:Thyroxine