Hello and welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. The thyroid hormone replacement therapy in kids and teens is crucial to ensure normal physical development and normal brain development, A low thyroid can interfere with normal growth and development and even put puberty on hold. The fatigue it causes can interfere with performance at school and leave kids without enough energy for sports and play, too. At the other side kids with hypothyroidism frequently experience a wide variety of neuropsychiatric sequelae. When Levothyroxine treatement start at 2 years old the recommended dosis is 5-6 mcg/kg PO qd.This dosis is gradually decreased in teen age and at 18 when the growth/puberty complete it is recommended the adult dosis(1,6 mcg/kg qd). After starting replacement thyroid hormone therapy, the TSH level should be measured in 3 to 6 weeks and the dosage adjusted accordingly. Successful treatment with thyroid replacement usually reverses the effects of hypothyroidism, although the psychiatric and neurologic sequelae may take longer to resolve. In your daughter case,my explanation is that when she had 3,5 tb qd ,probably she developed hypothyroidism because of lower dosis and in these circustances we can explain her Psychological problems. The only way to cope with psychological changes while treating thyroid disorder is to take both Thyroid hormone replacement therapy and the specific medicines related to Psychosis. My advice is to discuss with your daughter s treating doctors(the endocrinologist and the psychiatrist) about the right dosage(accorgind to TSH result for Levothyroxine) and the follow up of her conditions. Hope i have answered to your question. Let me know if i can assist you further.