Further Study of Factors Affecting the Metabolic Clearance Rate of Testosterone in Man 1

A B S T R A C T We have attempted to measure the metabolic clearance rates (MCR) and the transfer factors of estradiol (E2) and estrone (El) during 2-hr and 12-hr infusions. When estradiol-3H was infused for 2 hr, apparent equilibrium was reached at 70 min; the 12-hr infusions showed that plasma estradiol-3H levels increased slowly throughout the infusion. When estrone-3H was infused, constancy of estrone-3H levels was not attained in either the 2-hr infusions or in the two 12-hr infusions. The tritium level in the metabolite of the infused estrogen did not become constant in 50% of the short infusions and increased during all the long infusions. Thus, the conversion ratios CE1E2 and CE2E1 continually changed and transfer factors could not be calculated.The apparent "MCR'S" calculated on the basis of the 2-hr studies expressed as liters/24 hr per m2 4SD were:''MCRE1' (women) 980 494, (men) 1170 :195; "MCRE2" (women) 615 ±17, (men) 830 ±30. The estradiol "MCR's" differed significantly between men and women. "MCRE2" was the same using either estradiol-'4C or -3H and was unchanged by the infusion of 170 ,g of estradiol daily. Postmenopausal women had estrogen "MCR's" in the same range as premenopausal women. Excess glucocorticoids increased the "MCRE2."

Section: Ze2contrasting

confidence: 48%

Section: Ze2mentioning

confidence: 99%

See 1 more Smart Citation

A study of estrogen metabolic clearance rates and transfer factors

Hembree¹,

Bardin²,

Lipsett³

1969

“…In view of the results reported by others (23), and since we only have one such experiment, a valid explanation for this finding must await more extensive studies. Nevertheless, acute and chronic changes produced by testosterone could either be due to an increase in hepatic blood flow or to induction of enzymes involved in the metabolism of testosterone.…”

Section: Conversion Ratios and [P] Values The Conversionmentioning

confidence: 66%

Metabolism of testosterone and androstenedione in normal and ovariectomized women

Abraham¹,

Lobotsky²,

Lloyd³

1969

A B S T R A C T Metabolic clearance rates of testosterone (MCRT) and androstenedione (MCRA) were determined twice during the same cycle in six normal women, using a constant infusion of testosterone-2H and androstenedione-"C. Nonlabeled steroids served as internal standards. Plasma concentrations of testosterone (iT) and androstenedione (iA) were measured, and the blood production of testosterone (PBT) and of androstenedione (PBA) were calculated. The interconversions of these two steroids were also estimated. Six ovariectomized women were studied in the same manner. For testosterone, the mean i in the normal women was not significantly different from that in the ovariectomized subjects, whereas the MCRT and PET were significantly lower in the ovariectomized subjects. For androstenedione, the mean MCRA values of the two groups of subjects were not different, whereas the iA and PBA in the normal women were about double those in the ovariectomized subjects. In comparing the follicular and luteal phases of the menstrual cycle in four of six subjects there was no difference in iT, MCRT, or PBT, whereas iA, MCRA, and PBA were increased in the luteal phase. In one ovariectomized woman infused with testosterone and androstenedione at physiologic levels, MCRT doubled but MCRA remained the same. After six wk on estrogen, the same subject did not show any change in MCRT after infusion of testosterone. It is suggested that MCRT depends on PBT and on plasma binding of testosterone which is partly estrogen dependent.

“…The following subjects were studied: three normal men and one normal woman (subjects 1-4, age [21][22][23]. Patient 5 (age 26) had been successfully treated for choriocarcinoma 12 months previously, and patient 6 (age 23) was receiving replacement doses of cortisol and 9a-fluorohydrocortisone after bilateral adrenalectomy for adrenal hyperplasia.…”

Section: Introductionmentioning

confidence: 99%

The metabolic clearance rate and origin of plasma dihydrotestosterone in man and its conversion to the 5α-androstanediols

Mahoudeau¹,

Bardin²,

Lipsett³

1971

128

A B S T R A C T Dihydrotestosterone metabolismThe conversion of plasma testosterone and androstenedione to dihydrotestosterone was studied in men and hirsute women. Approximately 4 and 2% of plasma testosterone and androstenedione, respectively, were converted to plasma dihydrotestosterone in both groups. From these observations it was determined that a major fraction of plasma dihydrotestosterone was derived from these plasma precursors rather than from glandular secretion.Both 5a-androstan-3a,17#8-diol (3a-diol) and 5a-an- drostan-3,8,17,i-diol (38-diol) (1) has been stimulated by recent suggestions that his potent androgen is an intracellular effector of testosterone action (1,2). Testosterone and androstenedione are metabolized to dihydrotestosterone (DHT) 1 in many tissues (3-7). The entry of this steroid into the plasma from these sources would contribute to total blood androgens. It was pertinent, therefore, to examine the conversion of plasma testosterone and androstenedione to plasma dihydrotestosterone in order to estimate the importance of secretion of DHT as compared with its peripheral production.