Gonadotrophin, growth hormone and prolactin secretion in children with primary hypothyroidism

We have studied eight children with primary hypothyroidism (6F, 2M) aged 6.7 to 14.2 years. The girls were prepubertal and the boys had early normal pubertal development. Overnight secretion of LH, FSH, TSH, PRL and GH, and ovarian ultrasound morphology were assessed before and up to 9 months after commencing thyroxine treatment. Serum FSH concentrations in all the girls were increased above LH levels and severe hypothyroidism was associated with reduced GH secretion. These abnormalities reversed with thyroxine treatment. The boys had less severe hypothyroidism and did not demonstrate abnormal gonadotropin or GH secretion. We conclude that primary hypothyroidism in childhood is associated with widespread disturbance of pituitary function, including increased FSH secretion often without signs of early sexual maturation.