Metabolic clearance rates and production rates of human luteinizing hormone (HLH) were determined in pre- and postmenopausal women by the constant infusion technique. Highly purified HLH-(131)I was infused into the fasting subjects at a constant rate. Serial plasma samples were obtained and the radioactive hormone was precipitated by a double antibody technique. Plasma HLH-(131)I levels reached equilibrium by 4 hr after the infusion started. Metabolic clearance rates were: 24.4 +/- 1.8 (mean +/- SE) ml/min in five normal premenopausal women; 23.3 +/- 1.1 ml/min in five normal women taking norethinodrel and mestranol; and 25.6 +/- 4.1 ml/min in four postmenopausal women. Endogenous plasma HLH levels measured in the same subjects by radioimmunoassay immediately before infusion were 32.0 +/- 9.6 mU/ml in the normal women, 16.8 +/- 3.2 mU/ml in the women on oral contraceptives, and 99.2 +/- 23.2 mU/ml in the postmenopausal women. The corresponding HLH production rates were: 734 +/- 170 mU/min in the normal women: 387 +/- 86 mU/min in the women on norethinodrel and mestranol; and 2400 +/- 410 mU/min in the postmenopausal women. The metabolic clearance rate did not change after ovariectomy in one women, but the production rate rose from 583 to 1420 mU/min. Based on previously reported bioassay values for pituitary content and urinary excretion of HLH, the estimated turnover of HLH in the pituitary is about once per day and less than 5% of the total HLH produced appears in the urine in a biologically active form.

Journal Article↗

PubMed1968

Radioimmunoassay for human follicle-stimulating hormone: physiological studies.

Most of the information concerning secretion changes in follicle-stimulating hormone (FSH) in humans has been gained with relatively insensitive bioassays of concentrates of pools of urine. We have developed a sensitive and specific radioimmunoassay for FSH that is 500-1000 times more sensitive than the rat ovarianweight augmentation assay and which is capable of quantifying FSH in small volumes of serum. Anti-FSH was prepared by immunizing rabbits with an impure FSH preparation. The majority of antisera showed complete inability to distinguish LH, TSH, and FSH, illustrating the immunological similarities of these hormones. One antiserum was specific when used in a radioimmunoassay. Potency estimates by bioassay were in good agreement, with a single exception, with those obtained with the radioimmunoassay for 10 FSH-containing preparations. Highly purified LH gave a higher potency by immunoassay than by bioassay. Sera from eugonadal men contained 5-25 mIU/ml; sera from castrate men contained over 30 mIU/ml. Sera from eugonadal women contained 7-25 mIU/ml during the follicular phase and 5-15 mIU/ml during the luteal phase of the menstrual cycle. Sera from castrate or postmenopausal women contained 40-250 mIU/ml. FSH was measured throughout the menstrual cycle in 19 women. The general pattern that emerged is summarized as follows: there is a small early follicular phase rise in FSH, and then FSH is relatively constant until mid-cycle; in the majority of women a mid-cycle rise of FSH occurs coincidentally to the mid-cycle LH ovulatory peak; during the luteal phase FSH levels are relatively constant and lower than during the follicular phase. Nonsequential oral contraceptives containing estrogen and progestogen abolish these changes and FSH concentrations remain low throughout treatment. Treatment of castrate men and castrate or postmenopausal women with high doses of oral estrogens results in a fall of FSH to levels found in eugonadal men or women, but not to undetectable levels. Children less than 5 yr of age had undetectable FSH (< 5 mIU/ml).

Adult↗

PubMed1968