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Editor,—We report an 11 years 8 months old girl with juvenile hypothyroidism and precocious puberty who failed to respond to thyroxine, growth hormone, and luteinising hormone releasing hormone (LHRH) analogue. The patient was considered to be hypothyroid for about two years before the therapy was started. She had a very low serum thyroxine concentration, a height SD score of −3 SD, and a bone age of 10 years 3 months. Her pubertal development was graded as Tanner stage IV of breasts and Tanner stage II of pubic hair. Her menarche occurred at the age of 10 years 3 months. The enlarged pituitary gland reduced in size with the thyroxine treatment (100 μg/day). In addition to thyroxine, she was treated for 31 months with an LHRH analogue (30 μg/kg, once a month) and growth hormone (0.5 U/kg/wk divided into six doses) to avoid the progression of puberty and improve the final height. She reached the final height at the age of 15 years 1 month (−2.8 SD), which was the same as before the treatment (fig1).
Minamitani et al reported that treatment with LHRH analogue and growth hormone in addition to thyroxine was successful in improving the final height and avoiding pubertal growth of patients with juvenile hypothyroidism in the prepubertal stage.1 Difference between the report of Minamitaniet al and our case is that our patient already had the advanced bone age relative to height age and the progression of puberty at the start of treatment, to which our failure to improve the final height with the combination therapy might have been ascribed. To improve the final height, we should have increased the dose of LHRH analogue and growth hormone. During the combination therapy, peak serum insulin like growth factor 1 was 710 ng/ml (normal: 370–896 ng/ml), and peak concentrations of LH and FSH were completely suppressed in response to gonadotropin releasing hormone. Although her menstruation was successfully suppressed, bone maturation was not inhibited.
We concluded that patients with juvenile hypothyroidism who are often found to be in progressive pubertal development may not be indicated for treatment with LHRH analogue and growth hormone. An early diagnosis may therefore be of utmost importance in improving the final height. In Japan, schoolchildren are biannually measured for height and weight. It is therefore strongly urged to educate school nurses to direct their attention to the evaluation of height measurements and also thelarche and to consult paediatric endocrinologists. Although a number of possibilities have been raised for failure in attainment of desired height in the patient, the early medical attention would have been expected to lead to the possible prevention of short stature.
This work was supported by grants from the Ministry of Health and Welfare of Japan, the Ministry of Education, Science, and Culture, the Japan Private School Promotion Foundation, and the Mami Mizutani Foundation.