Robert F. Williams

Medical hypophysectomy: II. Variability of ovarian response to gonadotropin therapy *

In an attempt to control individual variability of ovarian response to gonadotropin therapy, ovulatory monkeys received either pure follicle-stimulating hormone (FSH) or human menopausal gonadotropin (hMG), with or without gonadotropin-releasing hormone (GnRH) antagonist administration. Among females that responded to gonadotropin therapy, the GnRH antagonist reduced (P less than 0.05) the variability of serum estradiol patterns. Surprisingly, after pretreatment and concurrent administration of the GnRH antagonist, FSH alone was as effective as the FSH/luteinizing hormone (LH) mixture (hMG) in stimulating follicular maturation, even when serum LH levels were at or below the limits of detection. The results indicate that in a rapidly reversible hypogonadotropic state approaching a medical hypophysectomy, concurrent gonadotropin therapy produces a less varied ovarian response. The relative (un)importance of LH in the primate ovarian cycle seems diminished in the face of evidence that FSH alone, or in the presence of vanishingly small amounts of LH, supports follicular maturation and dynamic estrogen biosynthesis.

Pulsatile progesterone secretion: its relevance to clinical evaluation of corpus luteum function

Pulsatile progesterone (P) secretory patterns were characterized in rhesus macaques (nxa0=xa013) during the midluteal phase (cycle days 18 to 20) of the normal ovarian/menstrual cycle. Sixty high-amplitude (>xa01xa0ng/ml) P pulses were observed during a total of 169 hours of sampling. Typically, P pulses had an ultradian periodicity of 2 hours and were independent of detectable luteinizing hormone (LH) and prolactin (PRL) pulses in 70% of instances. LH pulses were associated with a concomitant P and PRL pulse in 100% to 80% of occasions, respectively. Pulsatile P release was augmented by exogenous cynomolgus monkey LH and suppressed by administration of a gonadotropin-releasing hormone antagonist. Two individuals with apparently normal ovulation and once daily plasma P concentrations within the normal range demonstrated a nonpulsatile P profile. These findings encourage clinical investigations to characterize pulsatile P secretion in normal women and patients in whom corpus luteum dysfunction is suspected.

Disparate effects of human chorionic gonadotropin during the late follicular phase in monkeys: normal ovulation, follicular atresia, ovarian acyclicity, and hypersecretion of follicle-stimulating hormone.

To investigate the paradoxical actions of human chorionic gonadotropin (hCG) on ovarian function, 1000IU of hCG were administered to monkeys during the late follicular phase of 16 menstrual cycles, either on day 9 or day 11 after the onset of menses. Retrospectively, hormone profiles indicated that 6 of 16 hCG treatments were given coincidentally with incipient gonadotropin surges. In the remaining 10 cycles, hCG was given prior to the initiation of spontaneous gonadotropin surges. No untoward effects of hCG were observed in monkeys treated coincidentally with, or after, the onset of spontaneous surges of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In the 10 cycles in which hCG was injected prior to initiation of endogenous gonadotropin surges, induced atresia of the expected dominant follicle was presumed from the absence of the anticipated midcycle elevations of serum 17β-estradiol, LH, and FSH, and lack of a luteal phase increase in progesterone concentration. Resumption of cyclic ovarian function was delayed significantly (P 3 weeks). Among these 5 monkeys, the concentrations of LH, estradiol, and progesterone were indistinguishable from those of the remaining 5, in which serum FSH concentrations did not change appreciably. The data indicate that, after the initiation of the preovulatory gonadotropin surges, the ovaries were not susceptible to these pharmacologic impairments induced by hCG. In contrast, when administered prior to initiation of the spontaneous FSH and LH surges, hCG induced (1) apparent atresia of the dominant follicle; (2) arrest of cyclic ovarian function lasting more than 3 weeks; and (3) in 5 of 10 monkeys, an altered modulation of tonic FSH secretion, independent of LH release, where serum FSH persisted at levels about 3-fold above normal.

Hyperprolactinemia in monkeys: Induction by an estrogen-progesterone synergy

To evaluate the synergistic effect of estrogens and progesterone on prolactin secretion, rhesus and cynomolgus monkeys in the early follicular phase received estradiol benzoate (100 microgram/kg/day, sc) alone for 14 days, then in combination with progesterone (subcutaneous silastic capsule) for an additional 14 days. Blood was drawn daily by femoral venipuncture under ketamine hydrochloride anesthesia (15 mg/kg). Similarly, this protocol for exogenous steroid treatment was employed in a monkey having a chronically indwelling (femoral insertion into the vena cava) cannula maintained by a vest and mobile tether apparatus; however, no anesthesia was used to obtain serum specimens. In addition, this assembly was applied to six monkeys to determine the acute effects of ketamine hydrochloride on prolactin secretion. Concentrations of prolactin, estradiol-17 beta, and progesterone in serum were determined by conventional radioimmunoassays. Under estrogen therapy alone, mean circulating prolactin levels declined from approximately 15 to less than 5 ng/ml; in contrast, the addition of progesterone caused an abrupt serum prolactin elevation, approximately 8-12 fold. This estradiol-progesterone course led to sustained hyperprolactinemia in the chronically catheterized monkey, whereas ketamine administration raised serum prolactin only briefly, the elevation lasting less than three hours after injection. These findings establish that an estrogen-progesterone synergy, separate from the transient effects of ketamine, induced hyperprolactinemia in cycling monkeys having prevailing levels of estrogen and progesterone near those characteristic of late gestation, when sustained prolactin elevations are observed normally.

Endocrine consequences of prolonged ovarian hyperstimulation: hyperprolactinemia, follicular atresia, and premature luteinization * †

Eighteen normal ovulatory cynomolgus (Macaca fascicularis) monkeys were given an extended fixed-dose regimen of human menopausal gonadotropin (hMG), which was followed by human chorionic gonadotropin (hCG) administration. Ovarian hyperstimulation developed in responsive subjects to various degrees. Based on their serum estradiol (E2) response, 16 were arbitrarily categorized as high responders (E2 greater than 1000 pg/ml), 3 were medium responders (E2 500 to 1000 pg/ml), and 2 were low responders (E2 150 to 500 pg/ml). Interestingly, one female did not respond to exogenous gonadotropin therapy. The endocrine consequences of prolonged ovarian hyperstimulation include (1) hyperprolactinemia in the luteal phase of 50% of responsive monkeys; (2) frequent atresia of growing follicles, marked by a precipitous decline in serum E2, despite continuous hMG therapy; and (3) seven monkeys with premature serum progesterone elevations up to 1 week before hCG injection, without an overt luteinizing hormone surge. Only 1 of 18 females manifested a typical midcycle luteinizing hormone surge during hMG/hCG treatment. These findings have physiologic implications that are relevant to ovulation induction and in vitro fertilization therapy in infertile women.

Ovulation induction using “pure” follicle-stimulating hormone in monkeys *

Recently we have demonstrated that administration of a pure follicle-stimulating hormone (FSH) preparation (Urofollitropin, Serono Laboratories, Inc., Randolph, MA) to normally cycling monkeys induces multiple follicular development. In these earlier studies, a spontaneous luteinizing hormone (LH) surge was uncommon; no attempt was made to induce ovulation with exogenous human chorionic gonadotropin (hCG). In this study, multiple follicular development and ovulation were induced in normally cycling monkeys by daily follicular phase administration of pure FSH followed by hCG. Short-term administration of pure FSH during the early or late follicular phase also induced multiple follicular development; however, multiple ovulations subsequent to a spontaneous LH surge never occurred. One monkey treated in the late follicular phase did demonstrate a spontaneous LH surge and single ovulation following late follicular phase FSH treatment. These findings suggest that administration of pure FSH alone, to enhance the natural ovarian cycle, may be useful for inducing multiple follicular development, but that ovulatory competence is usually dependent on exogenous LH/hCG.

Prevention of gonadotropin-releasing hormone antagonist induced luteal regression by concurrent exogenous pulsatile gonadotropin administration in monkeys * †

We studied the effects of a gonadotropin-releasing hormone (GnRH) antagonist given in midluteal phase. Monkeys received the antagonist (n = 6), [N-Ac-D-p-Cl-Phe1,2,D-Trp3,D-Arg6,D-Ala10]-GnRH: hydrochloride or vehicle (n = 5). Absent luteinizing hormone (LH) pulsatility, diminished progesterone (P) secretion (P less than 0.01), luteal phase truncation and premature menstruation were observed in all receiving the antagonist. To investigate the site of action, four females received pulsatile exogenous human menopausal gonadotropins (hMG) concurrently, whereby P secretion was sustained and premature menstruation was averted. Equivalent treatment using pure FSH, failed to sustain P levels and timely menstruation occurred, confirming the continuing dependence of the corpus luteum on LH. The antagonist acts by central suppression and in turn, diminishes P biosynthesis. LH is luteotropic, since pulsatile LH (hMG), not pure FSH, prevented luteolysis.

Histologic and hormonal documentation of the luteinized unruptured follicle syndrome

Histologic and hormonal documentation of a luteinized unruptured follicle that occurred during a spontaneous menstrual cycle in a rhesus monkey is presented. Frequent (every 2 hours) blood sampling to assess midcycle hormonal dynamics in the monkey with the luteinized unruptured follicle and in five monkeys with an ovulatory stigma revealed significant aberrations in the gonadotropin and steroid hormone profiles associated with a luteinized unruptured follicle. Although the midcycle 17 beta-estradiol surge was normal, the monkey with the luteinized unruptured follicle demonstrated (1) blunted midcycle bioassayable luteinizing hormone, immunoassayable luteinizing hormone, and follicle-stimulating hormone surges; (2) absence of disparity in the bioassayable luteinizing hormone: immunoassayable luteinizing hormone ratio during the gonadotropin surge; (3) absence of progesterone and 17 alpha-hydroxyprogesterone secretion during the gonadotropin surge; and (4) delayed and blunted rise in progesterone and 17 alpha-hydroxyprogesterone after the gonadotropin surge. These findings suggest that an impaired luteinizing hormone surge, perhaps mediated by insufficient midcycle progestin secretion, is one possible cause of the luteinized unruptured follicle syndrome.

Etiology of infertility in monkeys with endometriosis: Measurement of peritoneal fluid prostaglandins

To study the relationship between peritoneal fluid prostaglandins and infertility associated with endometriosis, we autografted endometrial or adipose tissue to the pelvic peritoneum in 21 monkeys. Peritoneal washings were collected prior to tissue transplantation and during a subsequent laparotomy performed for biopsy of the implants. Monkeys were mated and peritoneal washings were collected during three subsequent cycles. The content of prostaglandin F2 alpha (PGF2 alpha) in adipose tissue autografts was significantly less (p less than 0.05) than in endometrial tissue autografts. The PGF2 alpha concentration in peritoneal fluid increased significantly (p less than 0.05) only in monkeys that developed moderate or severe endometriosis. Prostaglandin E levels in tissue autografts or peritoneal fluid were similar in all animals. Infertility in monkeys with endometriosis was associated with luteinized unruptured follicles, luteal phase defects, and pelvic adhesions. Although PGF2 alpha concentrations in peritoneal washings obtained during these cycles were increased in comparison with those of ovulatory cycles, the difference was not significant. A relationship between spontaneous abortion and prostaglandin concentrations in peritoneal fluid was not established.

Selection and Maturation of the Dominant Follicle and Its Ovum in the Menstrual Cycle

The specialized investments of the growing preovulatory follicle, and its successor the corpus luteum, establish and maintain the changing hormonal milieu which nurtures the ovum through maturation, fertilization, and the initial stages of embryogenesis. Indeed, it is the ovarian cycle which modulates hypothalamic-pituitary function through both negative and positive feedback on gonadotropin release, as well as temporal regulation of proliferative and secretory phases within the uterus during the menstrual cycle. No wonder, then, that the sequelae to aberrancies during folliculogenesis (spontaneous or induced) include abnormalities of the cervical mucus, endometrium, circulating gonadotropins, the corpus luteum, and even the ovum. Accordingly, fertility in the female depends most fundamentally on an underlayment of intra-ovarian processes which account for timely follicular growth culminating in ovulation of a fertilizable oocyte.