Serum gonadotrophin levels during development in male, female and androgenized female rats and the effect of general disturbance on high luteinizing hormone levels.

Serum LH, FSH and prolactin levels were measured in blood samples which were obtained by decapitation from groups of female, neonatally androgenized female and male Wistar rats at 2-day intervals from birth to maturity. An increase in serum FSH levels was observed between 4 and 24 days of age in both the female and androgenized female groups, while a much later increase, between 28 and 44 days of age, occurred in the males. Serum prolactin contrast, serum LH levels were in general low in all three groups of animals, although very high levels (greater than 7 ng/ml) were recorded in 22 out of 168 females and 8 out of 192 males between 4 and 28 days of age, as well as in adult males; occasional high LH levels were also seen in the androgenized females. The nature of the high serum LH levels was investigated in anaesthetized and unanaesthetized immature females by serial blood sampling using a number of techniques. Unexpectedly, only three out of 58 animals had high LH levels: two of these showed an episodic form of LH release during which levels increased to peak values and then declined within a period of about 30 min. On investigation it was found that general disturbance within the 45 min before decapitation could inhibit high LH levels in females aged between 23 and 30 days.

An evaluation of the luteinizing hormone releasing hormone (LH-RH) test in patients with secondary amenorrhoea.

An analysis of the gonadotrophin response to an intravenous injection of LH-RH (50 mug) has been undertaken in 41 patients with secondary amenorrhoea. Thirty-five of the patients were free of any recognizable pathology to account for their amenorrhoea and apparently had a dysfunction of the hypothalamic-pituitary axis. In these patients, the gonadotrophin response to LH-RH was highly variable. There was in general a correlation between baseline plasma LH or FSH levels and their respective increments. There was no correlation, however, between basal oestrogen levels and gonadotrophin increments except in the case of those patients whose basal levels of plasma FSH were higher than those of LH and in those patients whose body weight was less than the ideal for the population. It appears that the gonadotrophin response to a single injection of LH-RH in the majority of patients with secondary amenorrhoea of unknown origin is too variable to be of use either as a diagnostic or prognostic tool.

Changes in the concentration of luteinizing hormone in plasma during development in the guinea-pig.

The concentration of LH in the plasma of guinea-pigs from day 50 of gestation to day 45 of postnatal life was assayed by radioimmunoassay utilizing a cross-reaction with anti-ovine LH antiserum. The effect of gonadectomy in infancy and in the adult upon the plasma concentration of LH was also studied. The LH concentration in the plasma of male or female foetuses was high immediately prenatally and fell at birth. High levels of LH were again detected in male, with a lesser increase in female, guinea-pigs over the first 10 days postnatally. Maternal plasma concentrations of LH remained consistently low. Removal of the gonads on days 0, 5, 10, 15, 25 or 35 of postnatal life, followed by blood collection at autopsy 10 days later, caused a significant rise in plasma LH content at all ages. The rise in plasma LH after gonadectomy in adults was less marked in male than in female guinea-pigs.