Concentrations of plasma luteinizing hormone in infants, children, and adolescents with normal and abnormal gonadal function.

Abstract

Extract: This communication reports the edevelopment of a sensitive, reproducible, and specific radioimmunoassay for luteinizing hormone (LH) in plasma and the application of this method to a cross-sectional survey of plasma LH concentrations in 243 infants, children, and adolescents with normal and abnormal growth and sexual development. One nanogram of Hartree purified human pituitary LH standard was immunologically equivalent to 13.7 mIU of the Second International Reference Preparation of Human Menopausal Gonadotropin. The lower limit of sensitivity of the assay varied between 0.025 and 0.05 ng/ml. Specimens of plasma containing <0.25 ng/ml (<3.7 mIU/ml) have been considered indistinguishable from ‘zero’.Plasma LH concentrations increased after 9 years of age in normal boys and after 6 years of age in normal girls. In males with constitutional delay in growth and development, LH levels were generally lower than in normal boys of comparable ages (figs. 3 and 4). The plasma LH concentration also increased with advancing sexual maturation (fig. 5).Levels of LH were <0.25 ng/ml in 15 of 18 males (6-20 years old) and in 10 of 11 females (6-19 years old) with hypopituitarism and documented lack of human growth hormone response to hypoglycemia. In three such patients, plasma LH concentrations correlated with their degrees of sexual maturation, but in a 16-year-old clinically prepubertal male, patient SA, with hypopituitarism secondary to a craniopharyngioma, LH levels higher than normal male values were noted.Plasma LH concentrations were 1.2 and 1.45 ng/ml in 2 of 3 girls less than 4 years old, with gonadal dysgenesis, and ranged between 0.33 and 3.6 ng/ml in 10 of 15 older patients with this diagnosis (table III). The plasma LH concentration was 1.7 ng/ml in a 3-month-old male pseudohermaphrodite. Plasma LH concentrations ranged between 0.38 and 0.88 ng/ml in five of seven children with true sexual precocity. In 13 of 15 girls with precocious thelarche, and in all of 10 patients with premature pubarche, LH levels were <0.25 ng/ml. The intravenous infusion of conjugated equine estrogens was followed by a prompt decline in polasma LH values in patient SA (fig. 6A,B,C). Administration of clomiphene citrate and cisclomiphene citrate increased plasma LH concentrations in normal males, but failed to do so in patients with hypopituitarism, including patient SA (fig. 7A,B). The intramuscular administration of medroxyprogesterone acetate was associated with suppression of plasma LH levels in two patients with true sexual precocity (fig. 8).Speculation: The hypothalamic-pituitary-gonadal axis is active in the prepubertal human subject, and is responsive to abnormal function in one segment of the system.