The pattern of hormonal changes just before ovulation was investigated in immature rats induced to ovulate with pregnant mare serum gonadotrophin (PMSG). Oestradiol levels in the blood reached a maximum 42\p=n-\52h after PMSG treatment and then decreased dramatically. Pituitary luteinizing hormone (LH) levels remained constant until the time of the critical period (50\p=n-\52h) and then fell significantly. Plasma LH levels started to rise at 52 h, reached a peak at 54 h and fell to undetectable levels by 58 h. Plasma progesterone also reached a peak at 54 h and then fell slowly over the following dark period. The timing and pattern of changes in plasma and pituitary hormone levels were very similar to those seen in adult rats before ovulation. There was a positive correlation between the dose of PMSG, the peak concentration of plasma oestradiol and the average number of ova shed.

Plasma progesterone levels were determined in 16 Beagle bitches undergoing a normal oestrous cycle. The mean concentration rose during oestrus and a peak of 20.3 ng/ml was attained early in metoestrus. Considerable variation was noted between animals in respect of the magnitude and timing of the progesterone peak. The time of the highest progesterone values ranged from three days before the end of oestrus to Day 21 of metoestrus. The mean hormone levels remained elevated throughout metoestrus. On the basis of the time of the initial rise in progesterone levels during oestrus and the oestrogen peak values in three animals, it is suggested that ovulation occurs on the first or second day of oestrus.

A double blind, controlled study was carried out in order to investigate the effects of administering spironolactone, 200 mg daily, to five healthy male volunteers. The patterns of change in plasma testosterone (T) and luteinizing hormone (LH) after spironolactone were significantly different from placebo and there were significant increases in the urinary excretion of androsterone (A), aetiocholanolone (EC) and total oestrogen. Urinary dehydroepiandrosterone (DHA) excretion, after an initial rise, declined progressively during the treatment period relative to controls. The results are discussed in the light of previous observations. It is concluded that treatment with spironolactone for 2--4 days will lead to a transient rise in plasma T and urinary DHA. Continued treatment (4--10 days) is thought to cause increased LH secretion, with normalization of plasma T and DHA excretion. These changes are accompanied by increased androgen catabolism and a slightly increased conversion of androgens to oestrogens. Healthy men may therefore show alterations in sex steroid metabolism if treated for several days with high doses of spironolactone.

SUMMARY Fourteen apparently healthy patients with ileostomies were found to be depleted of total exchangeable sodium and potassium, but had normal serum electrolyte concentrations and normal extracellular fluid and total body water volumes. The low exchangeable sodium and potassiums were thus primarily due to depletion of the intracellular compartment. There was no evidence of renal or intestinal conservation of these ions and plasma aldosterone, renin activity, and prolactin concentrations were normal in most and only moderately raised in a few. This apparent lack of any hormonal compensatory change to the electrolyte depletion may be due to the normality of the extracellular fluid volume and electrolyte concentrations. These patients seem to have adapted to a stable but depleted intracellular sodium and potassium state.

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