Patterns of Gonadotrophins and Gonadal Steroids throughout Life

Body mass index and high-density lipoproteins in Cherokee Indian children and adolescents

Native Americans are predisposed to insulin resistance and associated cardiovascular risk. Therefore, we studied whether BMI (body mass index) in a population of Cherokee children and adolescents is associated with HDL-C (HDL cholesterol), and the HDL particles Lp (lipoprotein) A-I and LpA-I:A-II. Subjects were grouped by BMI Z score quartiles within three gender-specific age brackets (5-9, 10-14, and 15-19 y) to examine for trends in lipoprotein and HOMA-IR (homeostasis index insulin resistance) values associated with adiposity and age. HDL-C decreased by BMI Z score quartiles in all three age groups for both genders. HDL-C, LpA-I, and LpA-I:A-II decreased with age in boys but not girls. Log HOMA-IR increased by BMI Z score quartiles in all three age groups for both genders. Linear regression modeling showed BMI Z score, triglyceride, and age to be associated with HDL-C, whereas HOMA-IR was associated with LpA-I:A-II but not with HDL-C or LpA-I. When waist circumference was substituted for BMI Z score in the same models, it was associated with HDL-C and both lipoprotein particles. In conclusion, adiposity is more associated with HDL-C lowering than with declines in the lipoprotein particles. HOMA-IR is less associated with HDL-C but may selectively influence LpA-I:A-II. Greater decreases in HDL-C, LpA-I, and LpA-I:A-II with age in boys is attributed to gender-specific hormonal changes. The early onset of HDL lowering in these Native American children and adolescents, particularly boys, warrants intervention strategies to prevent obesity and associated cardiovascular risk.

The role of sex hormones in the kinetics of chondrocytes in the growth plate

Sex hormones play important roles in the regulation of the proliferation, maturation and death of chondrocytes in the epiphyseal growth plate. We have investigated the effects of male castration on the cell kinetics of chondrocytes as defined by the numbers of proliferating and dying cells. The growth plates of normal rabbits and animals castrated at eight weeks of age were obtained at 10, 15, 20 and 25 weeks of age.

Our study suggested that castration led to an increase in apoptosis and a decrease in the proliferation of chondrocytes in the growth plate. In addition, the number of chondrocytes in the castrated rabbits was less than that of normal animals of the same age.

Puberty and genetic susceptibility to breast cancer in a case-control study in twins

BACKGROUND

Breast cancer is thought to result from excessive cumulative exposure to ovarian hormones. Different predictors of hereditary and sporadic breast cancer suggest different pathogenic mechanisms. Affected twin pairs may help to illustrate such differences.

METHODS

We obtained information from 1811 pairs of female twins, one or both of whom had breast cancer. The pairs were stratified according to concordance or discordance for breast cancer, zygosity, the presence or absence of a family history of breast cancer, and the presence of bilateral or unilateral disease. Disease-concordant monozygotic pairs were assumed to have a higher genetic susceptibility than other subgroups of pairs. Paired twins were compared with respect to age at puberty and other factors. We calculated adjusted odds ratios for the diagnosis of breast cancer when only one twin was affected and for the first of the two diagnoses when both were affected.

RESULTS

Within disease-discordant monozygotic pairs, the twin with an earlier onset of puberty did not have an increased risk of breast cancer (adjusted odds ratio, 0.8; 95 percent confidence interval, 0.6 to 1.2). Within disease-concordant monozygotic pairs, the twin with earlier puberty was much more likely to receive the diagnosis first (adjusted odds ratio, 5.4; 95 percent confidence interval, 2.0 to 14.5). In contrast, a later first pregnancy, lower parity, and later menopause within the pair were associated with an increased risk of breast cancer when one twin was affected but did not predict an earlier diagnosis when both were affected.

CONCLUSIONS

Within the most genetically susceptible subgroup of twin pairs, the strong influence of earlier puberty on the age at the diagnosis of breast cancer and the absence of linkage to hormonal milestones later in life suggest that most cases of hereditary breast cancer are not related to cumulative hormone exposure and that they may instead result from an unusual sensitivity to pubertal hormones. Associations between breast cancer and early menarche and those with reproductive milestones in adulthood may reflect different genotypes.

Reduced in-vitro fertilization of human oocytes from patients with raised basal luteinizing hormone levels during the follicular phase

A series of 62 women were managed in the University of Western Australia/PIVET Laboratory in-vitro fertilization programme. In 60 of them follicle growth was stimulated with clomiphene citrate with or without additional human menopausal gonadotrophin (hMG) and in two with hMG alone. Follicles were aspirated at laparoscopy following an hCG trigger injection and occasionally following a spontaneous luteinizing hormone (LH) surge. Oocytes were inseminated with 0.5 X 10(5)-10(5) sperm/ml 3-6 h later. A significant reduction (P less than 0.001) in the fertilization rate of mature oocytes was observed in those patients whose basal serum LH values were greater than 1 SD above the mean. Fifty-nine women subsequently had embryo transfer and of 10 clinical pregnancies, none occurred in those with elevated LH values. Reduced fertilization may be a reflection of premature oocyte maturation or ageing. This may have clinical implications in the management of some patients with unexplained infertility.

Maternal age, dizygotic twinning rates and age at menopause

The dizygotic (DZ) twinning rate declines after about maternal age 38 in Caucasian populations. Bulmer (1970) offered the explanation that waning ovarian function causes a decline in rates of double ovulation in originally twin-prone women. The present note suggests that some small part of the decline is caused by the earlier cessation of ovulation altogether in these women (presumably also as a result of waning ovarian function).