Abstract:
Primary and secondary osteoporosis in a female or a male mammal is treated by administering thereto a nitric oxide synthase substrate, a nitric oxide donor or both, optionally; in further combination with one or more of an estrogen, a progestin, an anabolic steroid. Nitric oxide substrate or donor also can be combined with one or more of other medications acting on bone, such as bisphosphonate, calcitonin, fluoride, androgen and other novel therapeutic agents. Either nitric oxide donor or substrate by itself or combination with other medications as described above can be used in both women and men, (preferably human) for prevention and treatment of osteoporosis and other metabolic bone disorders.

Description:
This is a divisional of application Ser. No. 08/616,470, filed Mar. 19, 1996, now U.S. Pat. No. 5,898,038. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a new method for treatment of osteoporosis and bone mineral disorders and to prevent bone loss, fractures and other abnormal clotting patterns, urogenital discomfort, prevention and treatment of cardiovascular diseases, and other conditions associated with the reduction in ovarian function in middle-aged women, with a nitric oxide synthase substrate (L-arginine), a nitric oxide donor, or both, alone or in combination with an estrogen and/or a progestin. Same compounds are also useful in men to decrease bone turnover and hence prevention and treatment of osteoporosis and for treatment of other metabolic bone disorders. 
     It is now well known, that hormone replacement therapy, such as estrogen treatment, improves or reverses the adverse effects of the cessation of sex steroid secretion by the ovaries during menopause. Estrogens have also been shown to prevent bone loss and improve a variety of functions including mood and psychological well-being in postmenopausal women. Estrogens have been shown to effect arterial tone and this may help to explain the reduction in hot flushes and decrease the cardiovascular mobility and mortality in postmenopausal women with estrogen replacement therapy. Unopposed estrogen therapy in postmenopausal women has been associated with endometrial hyperplasia and endometrial cancer. 
     Many studies have shown that the addition of progesterone to estrogen replacement therapy decreases the risk of endometrial cancer and even reverses endometrial hyperplasia. However, progestins are not without untoward side effects. Progestins may oppose the beneficial effects of estrogens on the cardiovascular system by inducing an adverse lipid profile in circulation. Progesterone may also counteract the beneficial effects of estrogen on vascular walls. Moreover, irregular or withdrawal bleedings are common with combined estrogen-progestin therapy. The current hormone replacement therapy (HRT) employs combinations of estrogen and progestins as in the case of most contraceptives. 
     One of the most exciting recent advances in biology and medicine is the discovery that nitric oxide which is produced by endothelial cells (as one of the endothelial derived relaxing factors) and that it is involved in the regulation of vascular tone, platelet aggregation, neurotransmission and immune activation in a favorable fashion (Furchgott and Zawaszki, 1980; Moncada, Palmer and Higgs, 1991; Ignarro, 1991). Nitric oxide is an important mediator of relaxation of the vascular smooth muscle (Moncada, Palmer and Higgs, 1991), was formerly known as EDRF (endothelin-derived relaxing factor) (Furchgott and Zawaszki, 1980; Moncada, Palmer and Higgs, 1991). Nitric oxide is synthesized by the oxidative deamination of a guanidino nitrogen of L-arginine by at least different isoforms of a flavin-containing enzyme, nitric oxide synthase (Moncada, Palmer and Higgs, 1991). Synthesis of nitric oxide has been shown to be competitively inhibited by analogues of L-arginine; N G  -nitro-L-arginine methyl ester (L-NAME), N G  -monoethyl-L-arginine (LMMA), N-iminoethyl-L-arnithine (L-NIO), L-monomethyl-L-arginine (L-NNMA) and L-N G  -methylarginine (LNMA) and Nw-nitro-L-arginine (L-NA). 
     Nitric oxide elevates levels of cGMP (1,3,5-cyclic guanosine monophosphate) within the vascular smooth muscle to produce relaxation and to reduce blood vessels tone (Moncada, Palmer and Higgs, 1991). Nitric oxide is also produced by macrophages and other immune cells. Nitric oxide binds to heme molecules and activates soluble guanylate cyclase (Ignarro, 1991) to increase the intracellular content of cGMP. It has long been recognized that nitrovasodilators, such as nitroprusside and nitroglycerine, inhibit vascular smooth muscle contractility to produce relaxation or to reduce vascular tone. These agents have been used since the late 1800&#39;s as vasodilators. However, only recently has the mechanism of action of these compounds been realized. Nitrovasodilators are now classified as nitric oxide donors because they are metabolized at the sites of interests to release nitric oxide (Moncada, Palmer and Higgs, 1991). The long-term use of nitrovasodilators may be regarded as substitution or a replacement therapy for a failing physiological mechanism. 
     There is a substantial body of evidence from animal studies that a deficiency in nitric oxide contributes to the pathogenesis of several diseases including hypertension, atherosclerosis and diabetes (Moncada, Palmer and Higgs, 1991) and toxemia of pregnancy (Yallampalli et al., 1993). There are many recent studies showing that the inhibition of nitric oxide synthase dramatically increases blood pressure. For example, the inhibition of nitric oxide synthesis with L-NNMA, L-NA or L-NAME leads to elevation of blood pressure and suggests that reduction of NO may contribute to the pathogenesis of hypertension (Moncada and Palmer, 1992). Furthermore, L-NAME-treatment potentiates the presser responses to angiotension, blunting of the release of nitric oxide by umbilical vessels (Pinto et al., 1991). The physiological decrease in blood pressure in pregnant spontaneous hypertensive rats was also shown to depend on endothelial derived nitric oxide (Ahokas, Merces and Sibal, 1991). Additionally, infusion of L-NA increases blood-pressure in pregnant rats and potentiates responses to vasopressors (Molnar and Hertelendy, 1992). These studies suggest that impaired nitric oxide synthesis may be an important mechanism in the etiology of several cardiovascular dysfunctions. 
     Nitric oxide synthesis and nitric oxide effector system (cGMP-dependent relaxation mechanism) are thought to be regulated by steroid hormones. There is an increase in cardiovascular diseases in women following menopause and these might be related to the decrease in sex steroids and thereby an alteration in nitric oxide. Female steroid hormones have been shown to modulate endothelium-dependent relaxation of vascular smooth muscle via nitric oxide. Estradiol treatment of rats causes increased nitric oxide production by vascular tissues, whereas progesterone counteracts this phenomenon (Miller and Van Houtte, 1991). It is well known that pregnancy is associated with an increase in cardiac output and a decrease in the resistance of virtually all the vascular beds in the body, although the mechanism of this phenomenon is not known. It is possible that this may be associated with changes in nitric oxide production or effects as a result of elevated steroid hormone levels. One important observation with regard to the above mechanism is that antiprogestins elevate blood pressure in animals and they produce hot flushes in humans, both males and females. The hot flushes may be mediated by the inadequate steroid action on the release of nitric oxide. Hot flushes are a primary symptom in menopausal, postmenopausal women and they are relieved by both estrogen and progesterone. 
     Studies described herein (see below) show that nitric oxide and the subsequent relaxation of the uterus is controlled by progesterone. The relaxation effects of the nitric oxide substrate, L-arginine, are greater in late pregnancy when progesterone levels are elevated in pregnant rats. Also there is greater uterine relaxation with L-arginine when uterine strips are taken from nonpregnant, ovariectomized rats treated with progesterone. In addition, treatment with pregnant rats with the nitric oxide inhibitor produces signs and symptoms of preeclampsia (e.g. hypertension, fetal retardation and proteinurea--the classical triad of preeclampsia). These symptoms are related to the decrease in vascular resistance and placental perfusion. Preeclampsia is also a well known model of accelerated atherosclerosis, as the decrease in placental perfusion is accompanied by increased fibrin deposition in placental vessels and increased thrombus formation. 
     EP 0441 119 A2 mentions the use of L-arginine in the treatment of hypertension and other vascular disorders. It suggests that the mechanism by which L-arginine is effective for this purpose is because it may be the physiological precursor of &#34;the most powerful endothelial-derived releasing factor, nitric oxide&#34;. The use of L-arginine in combination with other pharmaceutically active agents is not discussed in EP 0441 119 A2 publication. 
     This invention is also applicable to both primary and secondary osteoporosis in both females and males. In the female, the method of choice of treatment of primary osteoporosis is estrogen replacement therapy and in the case of male, the method of choice of treatment of primary osteoporosis is androgen replacement therapy. In both sexes for the secondary osteoporosis the underlying causative factors are numerous, including medication-induced osteoporosis (e.g., corticosteroids, antiepileptics, anticoagulants, thyroxine), immunosuppressant agents used in prevention of graft rejection and other disorders (cyclosporin), malignancies (e.g., multiple myeloma), immobilization-induced bone loss and other conditions of bone loss. 
     One aspect of the present invention provides a method for the prevention and treatment of primary and secondary osteoporosis, including medication induced-osteoporosis (i.e. corticosteroid-induced osteoporosis) and other metabolic bone disorders with a nitric oxide substrate and/or donor. 
     It is another object to provide such a method in which a progestational agent is used in combination with a nitric oxide substrate and/or donor for the prevention and treatment of osteoporosis and other metabolic bone disorders. 
     It is a further object to provide a method for the prevention and treatment of osteoporosis and other metabolic bone disorders using an estrogenic agent in combination with a nitric oxide substrate and/or donor. 
     It is another object to provide a method for prevention and treatment of osteoporosis and other metabolic bone disorders using a combination of an estrogenic agent and progestational agent with a nitric oxide substrate and/or donor. 
     Another object is to provide a method of prevention and treatment of male primary and secondary osteoporosis and other metabolic bone disorders using nitric oxide substrate and/or donor. 
     A further object is the provision of pharmaceutical compositions useful in practicing the methods of this invention. 
     Other objects will be apparent to those skilled in the art to which this invention pertains. Another object is to provide a method of prevention and treatment of male primary and secondary osteoporosis and other metabolic bone disorders using nitric oxide substrate and/or donor. 
     SUMMARY OF THE INVENTION 
     An important embodiment of this invention relates to a method of treating osteoporosis or other metabolic bone disorders in a menopausal or postmenopausal female. This embodiment comprises administering to a female manifesting the symptoms thereof, one or both of a nitric oxide synthase substrate, particlularly L-arginine and/or a nitric oxide donor, alone or in further combination with one or more of an estrogen, and a progestin in amounts effective to ameliorate osteoporosis symptoms. The amount of the estrogen is bioequivalent to approximately 2 mg per day of estradiol and the amount of the progestational agent administered is bioequivalent to 50-300 mg of injected progesterone. The amount of the nitric oxide synthase substrate (L-arginine), nitric oxide donor or both is effective to, respectively, either raise the blood level of circulating L-arginine in a patient to whom the composition is administered to at least about 10-50 nmole above the normally 50-100 nmole circulating levels or provide nitric oxide donor levels of about 1-1000 nM (varying according to the particular donor). This invention also relates to use of L-arginine or nitric oxide donor compounds in prevention and treatment of primary osteoporosis in men and in both sexes, secondary osteoporosis, including medication-induced osteoporosis (e.g., corticosteroid-induced osteoporosis) and other metabolic bone disorders. L-arginine is the only acknowledged substrate of nitric oxide synthase but any analogous substrates behaving in a similar manner are viewed as equivalent. 
     In a product aspect, this invention relates to a pharmaceutical composition comprising at least one of a nitric oxide synthase substrate such as L-arginine and a nitric oxide donor, alone or in further combination with one or more of a estrogen and/or progestin. The amount of the estrogen is bioequivalent to about 2 mg of estradiol. The amount of the progestin is bioequivalent to 50-300 mg. of injected progesterone. The amount of L-arginine per unit dosage is effective to either raise blood level of circulating L-arginine to at least about 1 nM above the normally 2-3 nM circulating levels. The nitric oxide donor lends are enough to raise the nitric oxide levels to about 1 to 1000 nM. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates the percentage changes of bone mineral density 6 weeks after each therapy as determined by dual energy x-ray absorptiometric bone scan of vertebrae. 
     FIG. 2 shows the weights of femurs in rats following various treatments for 6 weeks. 
     FIG. 3: Percentage changes of body weight over 6 weeks treatment period in various treatment groups. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The methods of this invention to treat osteoporosis and other bone mineral disorders in a menopausal/postmenopausal manunal and in men, preferably a human, who is manifesting the signs and/or symptoms or both (i.e. treatment of osteoporosis) thereof or who is a high risk candidate (prevention of osteoporosis) for doing so, e.g., as determined by appropriate clinical conditions. 
     Because these abnormal conditions of bone loss and other metabolic bone diseases in both sexes are produced by or aggravated by subnormal nitric oxide synthesis, both nitric oxide synthase substrate and donors, (e.g., L-arginine, and nitric oxide donors, e.g., sodium nitroprusside, nitroprusside, nitroglycerine, SIN-1, isosorbid mononitrate and isosorbid dinitrate) are useful for ameliorating the symptoms thereof and, in one aspect of the method of this invention, a combination of both are employed. 
     In the case of female, for both primary and secondary osteoporosis an added effect is achieved when the nitric oxide substrate and/or nitric acid donor is administered concurrently with an estrogen and/or progestational agent. Thus, the method aspect of this invention and the pharmaceutical composition aspect of this invention employs a nitric oxide donor and/or a nitric oxide synthase substrate such as L-arginine individually or together with an estrogen and/or a progestin, progesterone or norgestrel, or other agents that affect bone metabolism including bisphosponates, calcitonin, fluoride. 
     In the case of a male, for both primary and secondary osteoporosis, an added effect is achieved when the L-arginine and/or nitric oxide donor is administered concurrently with an androgen. Thus, the method aspect of this invention and the pharmacological composition aspect of this invention employs one or both of a nitric oxide donor and a nitric oxide synthase substrate with an androgen or other agents that affect bone metabolism such as, e.g., bisphosphonates, calcitonin, fluoride, and anabolic steroids. 
     Examples or combinations of active agents which can be administered concurrently with a nitric oxide substrate and/or nitric oxide donor are estrogens and progestins (see below). 
     Examples of dosage ranges of typical NO-substrates and NO-donors (per os) are: 
     
         ______________________________________Total dose______________________________________L-Arginine        500 mg - 10 g p.o.  Sodium Nitroprusside range 500-2000 ug/kg/day  Nitroglycerine 0.5-10 mg  Isosorbid mononitrate 10-100 mg  Isosorbid dinitrate 10-100 mg______________________________________ 
    
     The following are typical oral dosage ranges of active agents of the estrogen and progestin with the nitric oxide substrate or donor: 
     Estrogens: a daily dose bioequivalent to about 1 to 2 mg per day, e.g., Premarin R, Wyeth-Ayerst, 0.625 mg/day, estradiol valerate, 50 ug/day transdermally, vaginal estradiol creams, 1.25 mg/day and vaginal estradiol rings, 0.2 mg/day. 
     Progestins: A daily dose bioequivalent to 50-300 mg of progesterone/day, e.g., an injectable suspension of medroxyprogesterone acetate to provide a weekly dose of thereof of 100-1000 mg or tablets or dragees providing an oral dose thereof of 5-10 mg/day, an injectable solution of hydroxyprogesterone caproate which provides a weekly dose of 250-500 mg; tablets, capsules or dragees of northindrone acetate which provide a daily dose of 5-20 mg. 
     Other examples of estrogens and progestins are listed below: 
     Oral &#34;natural&#34; estrogens used in hormone replacement therapy currently available in the UK. 
     
         ______________________________________                         Dose  Product Composition (mg per day)______________________________________Climaval (Sandoz)        Estradiol valerate                         1 or 2  Progynova (Schering) Estradiol valerate 1 or 2  Harmogen (Abbott) Piperazine oestrone sulfate 1.5 or 2.5  Hormonin (Shire) Estradiol 0.6   + Estrone   + Estriol  Premarin (Wyeth-Ayers) Conjugated equine 0.625 or   Estrogens 1.25 or 2.5______________________________________ 
    
     Commercially available combination calendar packs or hormone replacement therapy. 
     
         ______________________________________Product Generic composition______________________________________Estrapak   Estradiol 50 μg per day (28 days, 8 patches)  Prempak-C +  Trisequens Norethisterone acetate 1 mg per day (12 days)  Trisequens conjugated equine oestrogens 0.625 mg per day (28 days)    forte +  Cyclo- Norgestrel 0.15 mg per day (12 days)  progynova conjugated equine oestrogens 1.25 mg per day (28 days)     +   Norgestrel 0.15 mg per day (12 days)   Estradiol 2 mg per day + oestriol 1 mg per day (22 days)   +   Norethisterone acetate 1 mg per day (10 days)   Estradiol 2 mg per day + oestriol 0.5 mg per day (6 days)   Estradiol 4 mg per day + oestriol 2 mg per day (22 days)   +   Norethisterone acetate 1 mg per day (10 days)   Estradiol 1 mg per day + oestriol 0.5 mg per day (6 days)   Estradiol valerate 1 mg per day (21 days)   +   Levonorgestrel 0.25 mg per day (10 days)   Estradiol valerate 2 mg per day (21 days)   +   Levonorgestrel 0.5 mg per day (10 days)______________________________________ 
    
     Daily doses of progestogens taken for 12 days per month in patients receiving oral or transdermal estrogens. 
     
         ______________________________________Norethisterone       0.7-2.5 mg per day  Medroxyprogesterone acetate 10 mg per day  Norgestrel 150 μg per day  Dydrogesterone 10-20 mg per day______________________________________ 
    
     Bisphosphonates: 
     Any of the available pharmaceutical preparations of bisphosphonates, i.e. Disodium etidronate 5-10 mg/kg BWt for 14 days in every 90 days, Alendronate 10 mg, once daily and other newer preparations such as Pamidronate, Clodronate, and Residronate. 
     Calcitonin: 
     Any of the available pharmaceutical preparations of calcitonin, i.e. salmon, eel or human calcitonins, dosage range 10-200 i.u., daily, parenteral or nasal route. 
     Anabolic steroids: 
     Any of the available pharmaceutical preparations of anabolic steroids, i.e. Nondrolone decaonate 50 mg. 1/M injection every 3 weeks. 
     Androgens: 
     Any of the available pharmaceutical preparations of Testosterone (100 mg, 1/M, monthly) or its analogs. 
     Fluoride: 
     Any of the available pharmaceutical preparations of fluoride, e.g., sodium fluoride, 10-50 mg, once daily. 
     The pharmacologically active agents employed in this invention can be administered in admixture with conventional excipients, i.e., pharmaceutically acceptable liquid, semi-liquid or solid organic or inorganic carriers suitable, e.g., for parenteral or enteral application and which do not deleteriously react with the active compound in admixture therewith. Suitable pharmaceutically acceptable carriers include but are not limited to water, salt solutions, alcohols, vegetable oils, polyethylene glycols, gelatin, lactose, amylose, magnesium stearate, talc, silicic acid, viscous paraffin, perfume oil, fatty acid monoglycerides and diglycerides, pentaerythritol fatty acid esters, hydroxy methylcellulose, polyvinyl pyrrolidone, etc. 
     The pharmaceutical preparations can be sterilized and if desired mixed with auxiliary agents, e.g., lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, coloring, flavoring and/or aromatic substances and the like which do not deleteriously react with the active compounds. 
     For parenteral application, particularly suitable are solutions, preferably oily or aqeous solutions, as well as suspensions, emulsions, depot preparations or implants, including suppositories, creams, ointments, and transdermal patches. 
     In a preferred aspect, the composition of this invention is adapted for ingestion. For enteral application, particularly suitable are unit dosage forms, e.g., tablets, dragees or capsules having talc and/or a carbohydrate carrier or binder of the like, the carrier preferable being lactose and/or corn starch and/or potato starch; particulate solids, e.g., granules; and liquids and semi-liquids, e.g., syrups and elixirs or the like, wherein a sweetened vehicle is employed. Sustained release compositions can be formulated including those wherein the active compound is protected with differentially degradable coatings, e.g., by microencapsulation, multiple coatings, etc. 
     Suitable for oral administration are, inter alia, tablets, dragees, capsules, pills, granules, suspensions and solutions. Each unit dose, e.g., each tablespoon of liquid or each tablet, or dragee contains, for example, 0.1-1000 mg of each active agent. 
     Solutions for parenteral administration contain, for example, 0.01-1% of each active agent in an aqueous or alcoholic solution. 
     The nitric oxide substrate and/or donor can be administered as an admixture with agents described above and any other optional active agent of as a separate unit dosage form, either simultaneously therewith or at different times during the day from each other. 
     The combination of active agents is preferably administered at least once daily (unless administered in a dosage form which delivers the active agents continuously) and more preferably several times daily, e.g., in 2 to 6 divided doses. The typical dose is about 0.5 to 1000 mg of each active agent, although some less active agents, e.g., L-Arginine, require much higher oral dosages, e.g., 500 to 10,000 mg, and others, e.g., sodium nitroprusside, require lower doses, e.g., 500-2000 ug/kg/day. Doses for nitroglycerine typically are orally 2.5 mg 2× daily; sublingually, 0.8 mg 1-4× daily; and transdermally via patch or cream, 0.2-0.4 mg/hr. Since the LD 50 dosages of most of these active agents is known in the prior art, a lower dosage regimen can be initiated and the dosage increased until a positive effect is achieved or a higher dosage regimen can initially be employed, e.g., in a crisis situation, and the dosages regulated downward as relief from the symptoms is achieved. Combinations of agents can be employed either continuously or sequentially. 
     In humans, L-arginine, estradiol, and progesterone (or bioequivalent of another progestin) should be given in a ratio which produces blood plasma levels of about 50-200 nmolar L-arginine, 500 to 1000 nmolar of estradiol, and 30-100 nmolar progesterone. 
     FIG. 1 illustrates the percentage changes of bone mineral density (BMD) 6 weeks after each therapy as determined by dual energy x-ray absorptiometric bone scan (DXA) of vertebrae. OVX=ovariectomy, E 2  =estrogen treated, LN=L-NAME treated, NG=nitroglycerine treated. Values are mean±SEM for 5 animals per group. Comparisons were made against ovariectomized rats (reference, OVX control) * P&lt;0.05, * * P&lt;0.02. For between group comparison the changes of BMD were calculated from the baseline measurements and expressed as percentages. As expected, the increase in BMD over the 6 week period in OVX rats was substantially lower (P&lt;0.02) than control sham-operated animals. Supplementation with E 2  completely reversed the effects of OVX on BMD, and the BMD was similar to that seen in sham-operated rats (i.e., control group). The addition of L-NAME was no further detrimental to the reduction in bone mass in OVX rats. However, the supplementation of E 2  in the presence of L-NAME completely failed to increase the BMD, in comparison to the OVX rats that received E 2  replacement. On the other hand, OVX rats that received NO donor managed to increase their BMD, similar to the rats who received E 2  replacement. The BMD in these two groups were similar to that in sham OVX rats, and the combination of E 2  and NO donor (NG) was not additive. 
     FIG. 2 shows the weights of femurs in rats following various treatments for 6 weeks. OVX=ovariectomy, E 2  =estrogen treated, LN=L-NAME treated, NG=nitroglycerine treated. Values are mean±SEM of right and left femurs from 5 animals per group. Comparisons were made against ovariectomized rats (reference, OVX control) * P&lt;0.05, * * P&lt;0.02. Femoral weights in OVX rats were substantially lower (P&lt;0.02) compared to sham-operated rats. The OVX-induced decrease in femoral weight was reversed by E 2  (P&lt;0.02), and also by NO donor treatment (P&lt;0.05). Again as with BMD, the E 2  effect to increase bone weight was blocked by L-NAME. NO donor alone restored the bone weights in OVX rats to the levels of E 2  treated OVX and sham-operated (control) rats. 
     FIG. 3: Percentage changes of body weight over 6 weeks treatment period in various treatment groups: OVX=ovariectomy, E 2  =estrogen treated, LN=L-NAME treated, NG=nitroglycerine treated. Values are mean±SEM for 5 animals per group. Comparisons were made against sham-operated rats (control) * P&lt;0.01. As expected OVX increased the body weight (due to the increase in total body fat, P&lt;0.01), and this was prevented by E 2  replacement alone or combination of estrogen with nitroglycerine. There was a tendency to lose some weight in L-NAME treated rats, but this was not statistically different to that observed with the sham-operated as well as estrogen treated rats. The weight of rats receiving NG alone had a similar increase in weight to that observed with OVX rats. 
     Surgical or natural menopause in women leads to both cortical and trabecular bone loss (S. J. Wimalawansa, 1993). Osteoporosis induced by OVX in rats has been widely used as a model of postmanopausal osteoporosis (D. N. Kalu, 1991) and has been validated as a clinically relevant model of human postmenopausal bone loss (Wronski et al., 1993). Our data demonstrate that, treatment with NO protects against the OVX-induced bone loss in adult female rats, as determined by DXA BMD measurements and bone weights. Our study shows that OVX for 6 weeks in 12 week old female rats decreased the increment of BMD (P&lt;0.02), and this was prevented with either E 2  replacement or administration of a NO donor. Moreover, it is likely that the E 2  -induced increase in BMD is dependent upon NO generation, since L-NAME completely obliterated the effects of estradiol. These studies indicate that exogenous NO can reverse the bone loss in estradiol-deficit animals and that estradiol-induced increase in BMD may be NO dependent. 
     Our studies suggest that exogenously administered NO may have therapeutic value in preventing the bone loss accompanying estrogen deficiency. These studies emphasize the potential importance of NO in regulating bone mineral metabolism. The fact that nitroglycerine, when administered topically can prevent bone loss suggests the possible usefulness of NO donors as therapy (i.e., simple and effective mode of delivery) for preventing bone loss in postmenopausal women. 
     Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the disclosure in any way whatsoever. The entire disclosure of all applications, patents and publications, cited above and below are hereby incorporated by reference. 
     EXAMPLE 1 
     Treatment of Osteoporosis and Other Metabolic Bone Disorders 
     To a nonpregnant human female (ca 45 years; 50-80 kg) displaying the signs of menopause or postmenopausal osteoporosis (primary and secondary) and/or other metabolic bone disorders, or to a human male displaying signs of osteoporosis and/or other metabolic bone disorders, administer L-arginine initially with a dose range of 0.5 to 20 g of L-arginine per os daily in three divided doses followed by a daily dose of 0.5 to 5 g of L-arginine. 
     EXAMPLE 2 
     Treatment of Osteoporosis and Other Metabolic Bone Disorders 
     To a female or male comparable to Example 1, administer daily 2×2.5 mg of nitroglycerine. 
     EXAMPLE 3 
     Treatment of Osteoporosis and Other Metabolic Bone Disorders 
     To a female comparable to Example 1, administer daily 0.5 to 20 g of L-arginine in combination with estrogen (e.g. estradiol valerate) 1-2 mg daily. 
     EXAMPLE 4 
     Treatment of Osteoporosis and Other Metabolic Bone Disorders 
     To a female comparable to Example 1, administer daily 2×2.5 mg nitroglycerine with a progestin (e.g. norgestrel) 150 μg per day. 
     EXAMPLE 5 
     Treatment of Osteoporosis and Other Metabolic Bone Disorders 
     To a male comparable to Example 1, administer daily 0.5 to 20 g of L-arginine in combination with suitable depot preparation of an androgen. 
     EXAMPLE 6 
     Treatment of Osteoporosis and Other Metabolic Bone Disorders 
     To a male comparable to Example 1, administer daily 2×2.5 mg nitroglycerine with a suitable depot preparation of an androgen. 
     EXAMPLE 7 
     Treatment of Osteoporosis and Other Metabolic Bone Disorders 
     To a female comparable to Example 1, administer L-arginine 0.5 to 20 g daily and/or a nitric oxide donor (e.g. nitroglycerine, 2×2.5 mg) daily with or without one of the following, an estrogen (e.g. estradiol valerate) 1-2 mg daily, or a progestin (e.g. norgestrel, at 150 μg per day) or an androgen, respectively. 
     The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants (bisphosphonate, calcitonin, anabolic steroids, fluoride) and/or operating conditions of this invention for those used in the preceding examples. From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.