Adrenal steroids as parameters of the bioavailability of MA and MPA

Glucocorticoid receptor and breast cancer

Stress enhances glucocorticoid (GC) synthesis, which alters inflammation and immune responses, as well as cellular proliferation and apoptosis in a number of tissues. Increasingly, stress has been associated with cancer progression, and in particular in breast cancer. Consequently, an operational glucocorticoid receptor system in breast tissue influences breast cancer development. In this review, we summarize the data on the GC/GR system in normal and tumoral breast tissue. We also review the molecular mechanisms by which GCs control apoptosis and proliferation in breast cancer models and how GCs alter the chemotherapy of breast cancer treatment when used in combination. Finally, we discuss the participation of GR in breast tumorigenesis under hormone replacement therapy.

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

The aim of this study was to investigate the effects of treatment with medroxyprogesterone acetate (MPA) on canine adenohypophyseal function. Five Beagle bitches were treated with MPA (10mg/kg, every 4 weeks) and their adenohypophyseal function was assessed in a combined adenohypophyseal function test. Four hypophysiotropic hormones (CRH, GHRH, GnRH, and TRH) were administered before and 2, 5, 8, and 11 months after the start of MPA treatment, and blood samples for determination of the plasma concentrations of ACTH, cortisol, GH, IGF-1, LH, FSH, prolactin, alpha-MSH, and TSH were collected at -15, 0, 5, 10, 20, 30, and 45 min after suprapituitary stimulation. MPA successfully prevented the occurrence of estrus, ovulation, and a subsequent luteal phase. MPA treatment did not affect basal and GnRH-induced plasma LH concentrations. The basal plasma FSH concentration was significantly higher at 2 months after the start of MPA treatment than before or at 5, 8, and 11 months after the start of treatment. The maximal FSH increment and the AUC for FSH after suprapituitary stimulation were significantly higher before treatment than at 5, 8, and 11 months of MPA treatment. Differences in mean basal plasma GH concentrations before and during treatment were not significant, but MPA treatment resulted in significantly elevated basal plasma IGF-1 concentrations at 8 and 11 months. MPA treatment did not affect basal and stimulated plasma ACTH concentrations, with the exception of a decreased AUC for ACTH at 11 months. In contrast, the maximal cortisol increment and the AUC for cortisol after suprapituitary stimulation were significantly lower during MPA treatment than prior to treatment. MPA treatment did not affect basal plasma concentrations of prolactin, TSH, and alpha-MSH, with the exception of slightly increased basal plasma TSH concentrations at 8 months of treatment. MPA treatment did not affect TRH-induced plasma concentrations of prolactin and TSH. In conclusion, the effects of chronic MPA treatment on adenohypophyseal function included increased FSH secretion, unaffected LH secretion, activation of the mammary GH-induced IGF-I secretion, slightly activated TSH secretion, suppression of the hypothalamic-pituitary-adrenocortical axis, and unaffected secretion of prolactin and alpha-MSH.

Osteoporosis associated with megestrol acetate

Megestrol acetate is a progestational agent for treatment of metastatic breast cancer and endometrial cancer. Megestrol has also been used as an appetite stimulant for patients with human immunodeficiency virus and malignancy who experience cachexia and wasting; also, megestrol can be beneficial in relieving hot flashes in women and men. Megestrol has been shown to have a glucocorticoidlike effect and has been associated with substantial suppression of plasma estradiol levels. We describe 2 patients who recently presented to our Metabolic Bone Disease Clinic with severe osteoporosis complicated by multiple vertebral fractures experienced while the patients were receiving high-dose megestrol therapy. The patients had evidence of adrenal axis suppression but recovered fully after megestrol was discontinued. We speculate that megestrol was an important factor in the development of osteoporosis and subsequent fractures. Further study is warranted to clarify the relationship between megestrol and its potential for adversely affecting the skeleton.

Mammary steroid metabolizing enzymes in relation to hyperplasia and tumorigenesis in the dog

Progesterone and estradiol play a crucial role in the control of mammary gland proliferation and tumour formation in the dog. However, little is known whether steroid metabolizing enzymes are present within the canine mammary gland that may play a modulating role in the bioavailability of progesterone and estrogen. In this study we investigated the expression of the steroid metabolizing enzymes 5alpha-reductase (type I and type II) and aromatase in relation to hyperplasia or tumorigenesis in the canine mammary tissue. The relative mRNA concentrations were examined by a semi-quantitative reverse-transcriptase PCR analysis (RT-PCR). In addition the affinity of dihydroprogesterone (5alpha-reduced metabolite of progesterone) for canine progesterone receptors was investigated. Quantification of the RT-PCR products revealed that in mammary tumours a significantly higher expression of aromatase is present in comparison to normal mammary tissue. Furthermore, significant decrease in expression of both aromatase and 5alpha-reductase type II enzymes was found in hyperplasic mammary tissue compared to tumours. The changes in expression of type II 5alpha-reductase and aromatase were highly correlated. 5alpha-Reduction of progesterone to dihydroprogesterone resulted in a six-fold less affinity for the canine progesterone receptor. It is concluded that hyperplasia is associated with a decreased expression of type II 5alpha-reductase and aromatase enzymes, whereas in tumours the opposite situation is found.

Progestin-induced growth hormone (GH) production in the treatment of dogs with congenital GH deficiency

The recent demonstration of the ability of progestins to induce the expression of the growth hormone (GH) gene in the mammary gland of dogs and cats opens possibilities for the treatment of some forms of GH deficiency with progestins. Therefore, one male and one female German shepherd dog with congenital dwarfism because of a pituitary anomaly were treated with subcutaneous injections of medroxyprogesterone acetate (MPA) in doses of 2.5-5.0 mg per kg body weight, initially at 3-wk intervals and subsequently at 6-wk intervals. In both dogs, body sizes increased and a complete adult hair coat developed. Undesirable side-effects were recurrent periods of pruritic pyoderma in both dogs and cystic endometrial hyperplasia with mucometra in the female dog. Parallel with the physical improvements, plasma insulin-like growth factor I concentrations rose sharply. Plasma GH concentrations tended to rise, but never exceeded the upper limit of the reference range. Nevertheless, one of the dogs developed slight acromegalic features, possibly because mammary GH, unlike pituitary GH, is released evenly throughout the day. Even moderate increases in circulating GH concentration may, therefore, give rise to overexposure. It is concluded that long-term treatment with MPA can be used as an alternative for heterologous GH in the treatment of congenital GH deficiency in the dog.

Binding specificity of medroxyprogesterone acetate and proligestone for the progesterone and glucocorticoid receptor in the dog

The use of the synthetic progestin medroxyprogesterone acetate (MPA) for estrus prevention in the dog can result in overproduction of growth hormone, suppression of plasma glucocorticoid levels, and the induction of mammary tumors. Proligestone (PROL) was claimed to be devoid of these unwanted side effects. In the present study, the binding characteristics of MPA and PROL for the canine progesterone receptor (PR) and glucocorticoid receptor (GR) were investigated. The apparent inhibition constants for the PR and GR of MPA and PROL were compared with those of progesterone, ORG 2058, and a number of corticosteroids. MPA and PROL had high affinities for both the PR and the GR. The rank order for displacement of the binding of the PR ligand [3H]ORG 2058 from the canine uterine receptor was: MPA approximately ORG 2058 > PROL > progesterone >> cortisol, dexamethasone, and spironolactone. The rank order for displacement of the specific binding of the GR ligand [3H]dexamethasone from the canine liver receptor was: dexamethasone > cortisol > MPA > PROL > progesterone >> aldosterone approximately spironolactone. The apparent inhibition constants of PROL for both the PR and the GR were approximately 10 times higher than those of MPA. The ratios of the inhibition constants for the GR and PR appeared to be equal for PROL and MPA. It is concluded that although MPA has higher affinities for the PR and GR than PROL, both progestins have a similar in vitro binding specificity, which is less than that of progesterone. These findings are consistent with suppression of the adrenal cortex and the induction of growth hormone secretion in the mammary gland after MPA and PROL treatment in dogs.

Effect of megestrol acetate on the human pituitary-adrenal axis

A few previous reports have suggested that megestrol acetate, a synthetic progestational agent frequently used as an antineoplastic drug, suppresses serum cortisol concentrations in humans. To explore this concept further, we prospectively performed several measurements of the pituitary-adrenal axis in patients receiving megestrol acetate (160 or 800 mg/day). The data from these evaluations demonstrate that megestrol acetate reversibly decreases serum cortisol concentrations in humans and that this effect seems to originate from a suppression of the pituitary-adrenal axis. Additional studies should be conducted to determine the implications of the low levels of serum cortisol.

A randomized comparison of megestrol acetate (MA) and medroxyprogesterone acetate (MPA) in patients with advanced breast cancer

The efficacy and side-effects of megestrol acetate and medroxyprogesterone acetate in postmenopausal patients with advanced breast cancer were compared in a prospectively randomized study. The dosage of MA was 2 X 80 mg p.o. or MPA 2 X 500 mg p.o. daily, given as a secondary hormonal treatment, mostly after previous treatment with tamoxifen. Ninety-eight patients entered the study and 92 were evaluable for effect, 48 patients on MA and 44 on MPA. Age, main tumor site and prior treatment were not different, but there was a preponderance of ER-negative tumors in the MA group. Responses appeared to be more frequent in the MPA-treated group (25% vs. 43%), predominantly in bone lesions, 12% for MA and 45% for MPA. Median progression-free survival was comparable, 15 vs. 10 months, and overall survival was not different (20 vs. 16 months). Toxicity was frequent, occurring in 83% vs. 74% of patients: increased appetite, nausea and dizziness in more than 20%, and a preponderance of pyrosis and breathlessness on MA and hot flashes, sweating and tremors on MPA. Cushingoid symptoms were present in about a quarter of the patients treated for more than 3 months. The occurrence of thrombo-embolic episodes and cardiovascular events was evenly distributed. Patients on MPA had more often increase in body weight, systolic blood pressure and serum creatinine than those treated with MA. It is concluded that MPA may be more effective for treatment of bone metastases, at the expense of more progestational side-effects. The occurrence of Cushingoid effects is frequent but similar in both arms, while the incidence of cardiovascular or thrombo-embolic events cannot be related to the use of either compound.