Receptor binding and signal transduction are dissociable functions requiring different sites on follicle-stimulating hormone.

Separate sites for glycoprotein hormone receptor binding and signal transduction have yet to be elucidated. In general, certain peptide regions are thought to be critical for receptor binding, whereas the oligosacharides are thought to be important for signal transduction. Using site-directed mutagenesis of FSH, we made selective amino acid substitutions and oligosaccharide alterations to try and identify specific sites mediating receptor binding distinct from signal transduction and vice versa. We substituted Lys or Asp for beta Arg35 in the purported receptor binding loop between cysteine-32 and -51, and we substituted Gln for alpha Asn52, alpha Asn78, beta Asn7, or beta Asn24, the attachment sites for each of the oligosaccharide side-chains. We determined the binding and signal-transducing activity of wild-type and mutant human FSH at the human FSH receptor, as recent data suggest that glycoprotein hormone-receptor interactions are species specific. The binding activities of FSH with Lys or Asp substituted for beta Arg35 were reduced 71% and 98%, respectively, but their signal transduction, at equivalent levels of binding activity, was unaffected. The binding activity of FSH lacking the oligosaccharide at alpha Asn52 was enhanced 2- to 3-fold, but its signal-transducing activity, at equivalent levels of receptor binding, was decreased 72%. In contrast, the binding and signal-transducing activities of FSH lacking the alpha Asn78, or alpha Asn7, or beta Asn24 oligosaccharide were unaffected. Thus, a specific amino acid (beta Arg35) is important for high affinity binding, but is not involved in signal transduction, whereas a specific oligosaccharide (alpha Asn52) is important for signal transduction, but is not required for high affinity binding. Therefore, receptor binding and signal transduction are dissociable functions involving different sites on the FSH glycoprotein.

The use of human recombinant gonadotropin receptors to search for immunoglobulin G-mediated premature ovarian failure.

Anti-FSH receptor antibodies, detected using animal systems, have been reported in a few patients with premature ovarian failure (POF). However, assays based on animal receptors may be inappropriate for detecting inhibiting antibodies in humans. Accordingly, we tested for interfering antibodies in patients with POF using a recombinant system expressing human (h) FSH and LH receptors. A mouse adrenal cell line transfected with the hFSH receptor (Y1-hFSHR) exhibits a dose-dependent increase in progesterone when exposed to hFSH. An embryonal kidney cell line transfected with the hLH receptor gene (hLHR-293) exhibits a dose-dependent increase in cAMP when exposed to hLH. We isolated immunoglobulins G (IgG) from 38 patients with POF and 14 normal women. We stimulated Y1-hFSHR and hLHR-293 cells with hFSH or hLH in the presence of these IgG and determined the resulting progesterone or cAMP response. The progesterone and cAMP responses obtained in the presence of IgG from patients with POF did not differ significantly from the responses in the presence of IgG from normal women. In contrast, antigonadotropin polyclonal antibodies isolated in the same manner as the above IgGs caused a greater than 90% reduction in the response of the Y1-hFSHR and hLHR-293 cells. We did not detect inhibitory antibodies in any of our 38 patients with POF. Therefore, if blocking antibodies interfering with gonadotropin-receptor interaction are a mechanism for POF, they account for a small minority of cases (< 8%).

Metabolic clearance rate and urinary clearance of purified beta-core.

We injected a highly purified preparation of the beta-core molecule, a fragment of hCG beta excreted in pregnancy urine, into five men and three women to determine its kinetic parameters, MCR, and urinary clearance. The beta-core molecule was distributed in an initial volume [1950 +/- 156 (mean +/- SEM) mL/m2 body surface area] approximately equal to the estimated plasma volume. Its disappearance was multiexponential on a semilogarithmic plot, with a rapid phase t1/2 of 3.5 +/- 0.7 min and a slow phase t1/2 of 22.4 +/- 4.2 min. The transit time (the mean time spent by a molecule of beta-core in transit) was 20.6 +/- 2.1 min. The MCR was 192.0 +/- 8.0 mL/min.m2 body surface area. About 5% of the injected dose of beta-core was excreted into the urine in the first 30 min after injection, and low levels of excretion persisted for up to 7 days. The urinary clearance rate of beta-core was 13.7 +/- 1.4 mL/min.m2, accounting for about 8% of the elimination of beta-core from the plasma. The beta-core immunoreactivity in serum and urine was characterized by gel filtration and three independent RIA systems to show that its properties were indistinguishable from those of the injected beta-core. Serum levels of beta-core in pregnant women were less than 0.2 ng/mL, while the amounts excreted in their urine were as much as 5 mg/day. Based on these clearance parameters of beta-core in normal subjects, less than 0.2% of the beta-core excreted in pregnancy urine is derived by urinary clearance of plasma beta-core. Therefore, more than 99% of the beta-core excreted in pregnancy urine is derived from beta-core in a compartment separate from plasma. In particular, these data indicate that there is relatively little placental secretion of beta-core into plasma and that placental secretion does not account for the vast majority of beta-core in pregnancy urine. These findings are consistent with previous data that point to renal parenchymal degradation of hCG and hCG beta as the major source of urinary beta-core in pregnancy.

Increased biological activity due to basic isoforms in recombinant human follicle-stimulating hormone produced in a human cell line.

FSH has four asparagine-linked oligosaccharides with variable sialic acid contents, so that FSH is not a single molecule, but a heterogeneous group of isoforms. These isoforms differ in their biological properties and their distribution changes in various physiological states, allowing the modulation of FSH activity. Recombinant human (h) FSH has been produced in Chinese hamster ovary cells and has an isoform profile similar to those of both pituitary FSH standard and purified urinary FSH. These FSH preparations, however, do not contain the full spectrum of FSH isoforms found in the circulation. Production of recombinant hFSH in a cell line with a different pattern of glycosylation could broaden its isoform profile and potentially alter its biological activity. Thus, we transfected human embryonal kidney cells (293) with the human alpha and FSH beta genes to produce recombinant hFSH (hFSH-293) and determined its biological activity in a rat granulosa cell bioassay. Although hFSH-293 was immunologically indistinguishable from pituitary FSH standard, its biological potency was 3- to 6-fold higher than those of two different pituitary FSH standards. To investigate this increased potency, we separated the isoforms of hFSH-293 by chromatofocusing and determined their biological potencies in the rat granulosa cell bioassay. The isoform profile of hFSH-293 demonstrated a greater number of basic isoforms than that of pituitary FSH standard. Several of these basic isoforms exhibited enhanced in vitro biological potency, accounting for the increased biological potency of hFSH-293. This pattern of high in vitro biological activity and more basic isoforms is analogous to the FSH circulating during GnRH stimulation, pubertal induction, and ovulation.

A potential novel mechanism for precocious puberty in juvenile hypothyroidism.

Some children with juvenile hypothyroidism exhibit unexplained precocious puberty. Interaction of TSH with the human FSH receptor (hFSH-R) is a possible pathophysiological mechanism for this syndrome that has not been explored due to the lack of hFSH-free TSH preparations and the scarcity of a suitable hFSH-R-based assay system. To devise an in vitro FSH bioassay suitable for exploring this mechanism, we expressed hFSH-R complementary DNA in COS-7 cells and stimulated them with recombinant hTSH (rec-hTSH). Rec-hTSH elicited a dose-dependent cAMP response in the in vitro hFSH-R bioassay; however, the concentration of rec-hTSH required for half-maximal stimulation was several logs greater than that of hFSH. Rec-hTSH acted as a competitive inhibitor of hFSH at the hFSH-R, indicating that hTSH and hFSH are acting through the same receptor, namely the hFSH-R. This provides a potential novel mechanism for the precocious puberty of juvenile hypothyroidism.

Oral gossypol in the treatment of metastatic adrenal cancer.

Medical treatment of metastatic adrenal cancer is largely unsuccessful and has considerable toxicity. We previously demonstrated the activity of the plant toxin gossypol against human adrenal cancers in nude mice. We therefore examined the efficacy and toxicity of oral gossypol as a treatment for adrenal cancer in humans. Twenty-one patients with metastatic adrenal cancer received oral gossypol at doses of 30-70 mg/day. Patients were monitored for side effects of gossypol, changes in hormone secretion, and tumor response. Eighteen patients completed at least 6 weeks of gossypol treatment. Three of these patients, whose tumors were refractory to other chemotherapeutic agents, had partial tumor responses (> or = 50% decrease in tumor volume) that lasted from several months to over 1 yr. One patient had a minor response followed by resection of her remaining disease, 1 patient had stable disease, and 13 patients had disease progression. Three patients died of their disease without receiving sufficient gossypol to achieve detectable drug levels, and were eliminated from the final analysis. The side effects of gossypol were generally well tolerated; the only serious side effect was abdominal ileus that resolved when the drug was temporarily withheld and restarted at a lower dose. We conclude that oral gossypol can be used relatively safely on an outpatient basis for the treatment of metastatic adrenal cancer. The response rate is similar to the other agents currently available for adrenal cancer, and responses were seen in patients who had failed other chemotherapeutic regimens. This study provides the first indication that gossypol may have activity against cancer in humans, suggesting the need for further investigation of gossypol as an antitumor agent.

Routine endocrine screening for patients with karyotypically normal spontaneous premature ovarian failure.

OBJECTIVE: To evaluate the usefulness of routine screening for other associated autoimmune endocrine disorders in patients with karyotypically normal spontaneous premature ovarian failure. METHODS: One hundred nineteen women with karyotypically normal spontaneous premature ovarian failure (FSH exceeding 40 mIU/mL) who desired fertility were evaluated at a tertiary care academic center by physical examination, measurement of serum free thyroxine and TSH, ACTH stimulation test, fasting serum glucose, 3-hour glucose tolerance test, measurement of serum electrolytes including total calcium, and measurement of serum vitamin B12. RESULTS: Twenty-two of 119 patients (18.5%) were known to have hypothyroidism and three were known to have Addison disease. Ten new cases of hypothyroidism and three new cases of diabetes mellitus were discovered. However, no new cases of adrenal insufficiency, hypoparathyroidism, or pernicious anemia were found. CONCLUSION: Screening for hypothyroidism and diabetes appears justified in those patients with karyotypically normal spontaneous premature ovarian failure who desire fertility. However, our findings suggest that in these patients, testing for other associated autoimmune endocrine disorders may be reserved for those with clinical indications.

Minimal androgenic activity of a new oral contraceptive containing norethindrone acetate and graduated doses of ethinyl estradiol.

The pharmacokinetics and androgenic activity of Estrostep, a new oral contraceptive providing low-dose estrogen in a graduated sequence with a constant dose of progestin, were characterized in an open-label, nonrandomized study in 17 normally cycling women treated for three cycles with Estrostep. Women received 1 mg of norethindrone acetate daily combined with 20 microg of ethinyl estradiol daily for the first 5 days (1/20), 30 microg of ethinyl estradiol daily for the next 7 days (1/30), and 35 microg of ethinyl estradiol daily for 9 days (1/35). No medication was given for 7 days in each cycle to allow for withdrawal bleeding. Serial blood samples for the measurement of ethinyl estradiol and norethindrone concentrations were collected on days 5, 12, and 21 of the third treatment cycle for the 1/20, 1/30, and 1/35 dose, respectively. Sex hormone-binding globulin (SHBG) and free testosterone were measured at baseline, on day 1 of cycles 2 and 3 (SHBG only), and on days 5, 12, and 21 of cycle 3. Mean steady-state plasma ethinyl estradiol and norethindrone concentrations increased over cycle 3. The increases in ethinyl estradiol concentrations were proportional to dose. The increases in norethindrone concentrations were related to ethinyl estradiol-dependent increases in SHBG concentrations, which were 218%, 253%, and 296% of baseline values on days 5, 12, and 21, respectively. Mean plasma free testosterone concentrations decreased 47%, 60%, and 64% below baseline on days 5, 12, and 21 of cycle 3, respectively. Graduated ethinyl estradiol doses combined with a constant norethindrone acetate dose progressively increase SHBG and decrease free testosterone, which overrides any theoretic concerns of androgenic activity of norethindrone acetate. Although true androgenic activity can be determined only by assessing endpoints such as acne, hirsutism, and lipids in large controlled trials, the observed changes in circulating SHBG and free testosterone concentrations indicate that Estrostep has little, if any, intrinsic androgenic activity.

Safety and immunogenicity of a novel nanoemulsion mucosal adjuvant W805EC combined with approved seasonal influenza antigens.

BACKGROUND: Improving the systemic and mucosal immune response following intranasal vaccination could enhance disease protection against respiratory pathogens. We assessed the safety and immunogenicity of a novel nanoemulsion mucosal adjuvant W(80)5EC combined with approved seasonal influenza antigens. METHODS: This was a first-in-human Phase I study in 199 healthy adult volunteers randomized to receive a single intranasal administration of 5%, 10%, 15% or 20% W(80)5EC, combined with 4 or 10 µg strain-specific Fluzone(®) HA, compared with intranasal PBS, intranasal Fluzone(®), or 15 ug strain-specific intramuscular Fluzone(®). Safety was evaluated by physical examination, laboratory parameters, symptom diaries, and adverse event reports. Serum HAI titers and nasal wash IgA were assessed at baseline as well as 28 and 60 days after vaccination. RESULTS: W(80)5EC adjuvant combined with seasonal influenza antigens was well tolerated without safety concerns or significant adverse events. The highest dose of 20% W(80)5EC combined with 10 µg strain-specific HA elicited clinically meaningful systemic immunity based on increases in serum HAI GMT and ≥ 70% seroprotection for all 3 influenza strains, as well as a rise in antigen-specific IgA in nasal wash specimens. CONCLUSIONS: W(80)5EC adjuvant was safe and well tolerated in healthy adult volunteers and elicited both systemic and mucosal immunity following a single intranasal vaccination.

Site-directed mutagenesis defines the individual roles of the glycosylation sites on follicle-stimulating hormone.

To determine the specific role of each follicle-stimulating hormone (FSH) oligosaccharide, we mutated Asn to Gln at each glycosylation site (alpha Gln52, alpha Gln78, alpha Gln52-78, beta Gln7, beta Gln24, and beta Gln7-24) to selectively inhibit oligosaccharide attachment. For wild-type and mutant FSH, we determined the binding affinity to homogenized rat Sertoli cells and the signal-transducing activity in cultured rat granulosa cells. The binding affinity of FSH lacking any one of the oligosaccharides was increased over wild-type FSH, while the signal-transducing activity of FSH lacking the oligosaccharide at alpha Asn52 (alpha Gln52 FSH) was markedly reduced, and that of FSH lacking either beta oligosaccharide (beta Gln7 and beta Gln24 FSH) was slightly reduced. At each FSH beta glycosylation site, we made a second amino acid substitution to inhibit glycosylation (beta Tyr9 and beta Tyr26) and an amino acid substitution that preserved glycosylation (beta Ser9 and beta Ser26). The amino acid sequence of the second beta subunit glycosylation site was important for signal transduction, regardless of the presence or absence of the oligosaccharide. Thus, while each FSH oligosaccharide has a similar impact on binding affinity, the alpha 52 oligosaccharide has a disproportionate role in signal transduction, and the amino acid sequence at beta Asn24 functions in both binding and signal transduction.

Mutations of the human thyrotropin-beta subunit glycosylation site reduce thyrotropin synthesis independent of changes in glycosylation status.

In recent studies, site-directed mutagenesis has been used to alter the tripeptide glycosylation recognition sequences of glycoprotein hormone subunits, thereby affecting their structure and function. However, it is not known whether these effects result from changes in glycosylation status, amino acid sequence, or both. We therefore studied the synthesis of wild-type and mutant recombinant human thyrotropins produced by transient transfection of a human cell line. Mutating the TSH-beta subunit glycosylation recognition sequence, Asn-Thr-Thr (codons 23-25), to either Gln-Thr-Thr or Asn-Thr-Tyr abolished subunit glycosylation, as demonstrated by the inability to incorporate 3H-carbohydrates. However, a third mutation (Asn-Thr-Ser) contained an intact glycosylation recognition sequence site, and was shown to retain glycosylation. The mutations that abolished TSH-beta subunit glycosylation resulted in greater than 90% decreases in TSH synthesis. However, the glycosylation recognition sequence mutant that retained beta subunit glycosylation exhibited a 70% decrease in TSH production. These decreases were not attributable to the intracellular accumulation of TSH or its free beta subunit. We also engineered two TSH-beta subunit mutations that did not alter the glycosylation recognition sequence. A glycine to arginine mutation adjacent to the glycosylation recognition sequence, in a region thought to be critical for heterodimer formation, abolished TSH production. In contrast, shortening the TSH-beta subunit carboxyterminus by six amino acids increased TSH synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Urine free cortisol in the high-dose dexamethasone suppression test for the differential diagnosis of the Cushing syndrome.

OBJECTIVE: To develop criteria for interpreting the high-dose dexamethasone suppression test using urine free cortisol as an end point for the differential diagnosis of the Cushing syndrome. DESIGN: Retrospective review. SETTING: Inpatient research ward. PATIENTS: Patients (118) with surgically confirmed causes of the Cushing syndrome: 94 with pituitary disease, 14 with primary adrenal disease, and 10 with ectopic adrenocorticotropic hormone (ACTH) secretion. MAIN OUTCOME MEASURES: The sensitivity, specificity, and diagnostic accuracy were determined for the high-dose dexamethasone suppression test using urine free cortisol and using 17-hydroxysteroid excretion. For each analysis, patients with pituitary disease were considered to be "diseased" and patients with nonpituitary disease were considered to be "non-diseased". The level of suppression that gave 100% specificity was determined for each steroid. RESULTS: The accuracy of urine free cortisol when used as an end point in the high-dose dexamethasone suppression test was equivalent to that of 17-hydroxysteroid excretion. At all levels of sensitivity and specificity, however, the degree of suppression of urine free cortisol used for the diagnosis of pituitary disease was greater than that of 17-hydroxysteroid excretion. The likelihood ratios for pituitary disease based on urine free cortisol suppression of greater than 50%, of greater than 80%, and of greater than 90% were 4.2, 10.1, and "infinite," respectively. Suppression of urine free cortisol greater than 90% or suppression of 17-hydroxysteroid excretion greater than 64% was associated with 100% specificity. When these criteria were combined, the percentage of correct predictions (102 of 118 [86%; 95% CI, 78% to 92%]) was higher than that obtained using either steroid alone (89 of 118 [75%; CI, 65% to 83%]) (P = 0.009) and higher than that obtained using the traditional criterion of 50% suppression for 17-hydroxysteroid excretion (95 of 118 [80%; CI, 71% to 87%]) (P = 0.016). CONCLUSIONS: In the high-dose dexamethasone suppression test, the degree of suppression of urine free cortisol used for the diagnosis of pituitary disease is greater than that traditionally used for 17-hydroxysteroid excretion. The diagnostic performance of the test is improved by measuring both urine free cortisol and 17-hydroxysteroid excretion and by requiring greater suppression of both steroids.

The diagnosis of acromegaly: value of inferior petrosal sinus sampling.

The early diagnosis of acromegaly may be difficult when serum levels of growth hormone are minimally elevated and imaging of the pituitary gland fails to show an adenoma. However, transsphenoidal surgery has the greatest chance of cure at this stage. We therefore investigated the value of sampling petrosal sinuses for measurement of growth hormone in this group of patients. Simultaneous bilateral sampling of the inferior petrosal sinuses to measure serum concentrations of growth hormone was performed in five patients suspected of having acromegaly but with nondiagnostic CT scans (n = 5) and MR images (n = 3) of the pituitary gland. Levels of growth hormone from the petrosal sinuses were five to 36 times greater than levels in the peripheral veins in all five patients, and three of four showed a marked response to growth hormone-releasing hormone. During transsphenoidal surgery, growth hormone-producing microadenomas were resected completely in four patients. In the fifth patient, a left-sided microadenoma had invaded the cavernous sinus and could not be resected completely. Lateralization of the adenomas within the pituitary gland on the basis of differences in levels of growth hormone between the two petrosal sinuses was not completely reliable. Elevated levels of growth hormone in selective samples from the inferior petrosal sinuses can help support an early diagnosis of acromegaly when peripheral growth hormone levels and imaging are not diagnostic.