Under the Securities Exchange Act of 1934
(Amendment No. 1)*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. o

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(1)  The Reporting Person is a party to certain agreements with the other stockholders of the Issuer (the “Separately Filing Group Members”), which agreements contain, among other things, certain voting agreements and limitations on the sale of his shares of stock. As a result, the Reporting Person may be deemed to be a member of a “group,” within the meaning of Section 13(d)(3) of the Act (as defined in this Schedule 13D), comprised of the Reporting Person and the Separately Filing Group Members. Shares listed as beneficially owned by the Reporting Person exclude shares held by any of the Separately Filing Group Members, as to which the Reporting Person disclaims beneficial ownership.

The percentage is calculated based upon 39,659,648 shares of the Issuer’s common stock, $0.0001 par value (the “Common Stock”), being deemed issued and outstanding, which consists of: (i) 879,370 shares of Common Stock that are issued and outstanding and (ii) an aggregate of 38,780,278 shares of Common Stock issuable upon conversion of all shares of Preferred Stock (after giving effect to the Subsequent Anti-Dilution Adjustment) (as defined in this Schedule 13D)) that are issued and outstanding, as disclosed in the Issuer’s Annual Report on Form 10-K, filed with the SEC on February 26, 2014, in the Series B-2 Stock Purchase Agreement (as defined in this Schedule 13D) filed as an Exhibit to the Issuer’s Current Report on Form 8-K filed with the SEC on February 21, 2014, and as disclosed to the Reporting Person by the Issuer separately.  Because shares of Preferred Stock vote together with Common Stock on an as-converted basis, such percentage reflects the Reporting Person’s voting percentage of the Issuer’s outstanding capital stock. If the percentage calculation was calculated in accordance with Rule 13d-3(d)(1) promulgated under the Exchange Act, excluding shares held by any of the Separately Filing Group Members, as to which the Reporting Person disclaims beneficial ownership, it would result in an applicable percentage of 7.4%.

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Schedule 13D (Amendment No. 1)

EXPLANATORY NOTE: This Amendment No. 1 to Schedule 13D (“Amendment No. 1”) amends the statement on Schedule 13D filed by the Reporting Person together with other holders of shares of capital stock of Radius Health, Inc. (the “Issuer”) with the Securities and Exchange Commission on January 27, 2012 (the “Original Schedule 13D”).  This Amendment No. 1 amends the Original Schedule 13D solely with respect to the Reporting Person identified herein and the shares of capital stock of the Issuer held by him.

Amendment No. 1 is filed to report an increase in the number of shares of capital stock and a change in the percentage of the outstanding shares of capital stock of the Issuer beneficially owned by the Reporting Person as a result of the purchase of shares of capital stock of the Issuer by the Reporting Person and by certain of the Separately Filing Group Members and the issuance of shares of capital stock of the Issuer to another Separately Filing Group Member pursuant to a stock dividend (each as further described in Item 3 below).  Each capitalized term used and not defined herein shall have the meaning assigned to such term in the Original Schedule 13D.  Except as otherwise provided herein, each Item of the Original Schedule 13D remains unchanged.

Item 3.  Source and Amount of Funds or Other Consideration

Item 3 is hereby amended and restated in its entirety as follows:

Pursuant to an Agreement and Plan of Merger dated April 25, 2011 (the “Merger Agreement”), by and among the Issuer (under its former name of MPM Acquisition Corp.), RHI Merger Corp., a Delaware corporation and wholly owned subsidiary of the Company (“MergerCo”), and Radius Health, Inc., a Delaware corporation (the “Former Operating Company”), MergerCo merged with and into the Former Operating Company, with the Former Operating Company remaining as the surviving entity and a wholly-owned operating subsidiary of the Issuer. This transaction is referred to as the “Merger.” The Merger was effective as of May 17, 2011, upon the filing of a certificate of merger with the Delaware Secretary of State.  At the effective time of the Merger (the “Effective Time”), the legal existence of MergerCo ceased and all of the shares of the Former Operating Company’s common stock, par value $.01 per share (the “Former Operating Company Common Stock”), and shares of the Former Operating Company’s preferred stock, par value $.01 per share (the “Former Operating Company Preferred Stock”), that were outstanding immediately prior to the Merger were cancelled and each outstanding share of Former Operating Company Common Stock outstanding immediately prior to the Effective Time was automatically converted into the right to receive one share of the Issuer’s Common Stock, par value $.0001 per share (the “Common Stock”) and each outstanding share of Former Operating Company Preferred Stock outstanding immediately prior to the Effective Time was automatically converted into the right to receive one-tenth of one share of the Issuer’s Preferred Stock, par value $.0001 per share (the “Preferred Stock”) as consideration for the Merger.  Each share of the Preferred Stock was initially convertible at the time of issuance thereof into ten (10) shares of the Common Stock.

Pursuant to a Stock Issuance Agreement (as defined below), Nordic Bioscience Clinical Development VII A/S (“Nordic”) agreed, on March 29, 2011, to purchase the equivalent of €371,864 of Series A-5 Preferred Stock of the Former Operating Company at $8.142 per share, and the Former Operating Company sold 64,430 shares of its Series A-5 Preferred Stock to Nordic on May 17, 2011 for proceeds of $525,154.  These shares were exchanged in the Merger for an aggregate of 6,443 shares of the Issuer’s Series A-5 Stock.

Following the Merger on May 17, 2011, the Board approved a transaction pursuant to which the Former Operating Company merged with and into the Issuer, leaving the Issuer as the surviving corporation (the “Short-Form Merger”). In connection with the Short-Form Merger, the Issuer relinquished its corporate name and assumed in its place the name “Radius Health, Inc.” The Short-Form Merger and

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name change became effective on May 17, 2011, upon the filing of a Certificate of Ownership and Merger with the Delaware Secretary of State.

On November 18, 2011, pursuant to the terms of that certain Series A-1 Convertible Preferred Stock Purchase Agreement (as amended, the “Series A-1 Stock Purchase Agreement”), dated as of April 25, 2011, among the Issuer and the investors referenced therein (the “Investors”), the Issuer issued an aggregate of 263,178 shares (the “Stage II Series A-1 Shares”) of its Series A-1 Convertible Preferred Stock, par value $.0001 per share (the “Series A-1 Stock”), to the Investors.  Such shares were issued in connection with the consummation of the Stage II Closing contemplated by the Series A-1 Stock Purchase Agreement at a purchase price of $81.42 per share resulting in aggregate proceeds to the Issuer of $21,427,952.76.  On December 14, 2011, pursuant to the terms of the Stock Purchase Agreement, the Issuer issued an aggregate of 263,180 shares (the “Stage III Series A-1 Shares” and together with the Stage II Series A-1 Shares, the “Series A-1 Shares”) of its Series A-1 Stock, to the Investors.  Such shares were issued in connection with the consummation of the Stage III Closing contemplated by the Series A-1 Stock Purchase Agreement at a purchase price of $81.42 per share resulting in aggregate proceeds to the Issuer of $21,428,115.60.

On April 23, 2013 and May 10, 2013, pursuant to the terms of that certain Series B Convertible Preferred Stock and Warrant Purchase Agreement (the “Series B Stock Purchase Agreement”), dated as of April 23, 2013, among the Issuer and the investors referenced therein (the “Series B Investors”), the Issuer issued to the Series B Investors (i) an aggregate of 701,235 shares (the “Series B Shares”) of its Series B Convertible Preferred Stock, par value $.0001 per share, and (ii) warrants to purchase, for an initial exercise price of $6.142 per share, up to an aggregate of 1,753,091 shares of Common Stock (the “Warrants” and together with the Series B Shares, the “Series B Securities”).  Such Series B Securities were issued in connection with the consummation of the Initial Closing and the Second Closing contemplated by the Series B Stock Purchase Agreement in exchange for aggregate proceeds received by the Issuer of $43,069,853.70.  The issuance of the Series B Securities resulted in an adjustment to the conversion price (the “Initial Anti-Dilution Adjustment”) at which each share of the Issuer’s Series A-1 Stock, Series A-2 Convertible Preferred Stock par value $.0001 per share (the “Series A-2 Stock”), and Series A-3 Convertible Preferred Stock, par value $.0001 per share (the “Series A-3 Stock”), is convertible into shares of Common Stock.  As a result of the Initial Anti-Dilution Adjustment, the effective conversion price of each share of Series A-1 Stock, Series A-2 Stock and Series A-3 Stock was reduced from $8.142 to $7.627.  Accordingly, following the issuance of the Series B Securities, each share of Series A-1 Stock, Series A-2 Stock and Series A-3 Stock was convertible into 10.675 shares of Common Stock.

On December 31, 2013, the Board declared a dividend (the “Series A-6 Dividend”) of seventy-seven (77) shares of Series A-6 Stock on and in respect of each share of Series A-5 Stock outstanding at the close of business on such date, resulting in the issuance to Nordic on such date of 496,111 shares of Series A-6 Stock.  Each share of Series A-6 Stock is convertible into ten (10) shares of Common Stock.

On February 14, 2014, February 19, 2014 and February 24, 2014, pursuant to the terms of that certain Series B-2 Convertible Preferred Stock and Warrant Purchase Agreement (the “Series B-2 Stock Purchase Agreement”), dated as of February 14, 2014, among the Issuer and the investors referenced therein (the “Series B-2 Investors”), the Issuer issued to the Series B-2 Investors, including the Reporting Person, (i) an aggregate of 417,615 shares (the “Series B-2 Shares”) of its Series B-2 Convertible Preferred Stock, par value $.0001 per share, and (ii) warrants to purchase, for an initial exercise price of $6.142 per share, up to an aggregate of 1,044,039 shares of Common Stock (the “New Warrants” and together with the Series B-2 Shares, the “Series B-2 Securities”).  Such Series B-2 Securities were issued in connection with the consummation of the Initial Closing and a Subsequent Closing contemplated by the Series B-2 Stock Purchase Agreement in exchange for aggregate proceeds received by the Issuer of $25,649,913.30.  The issuance of the Series B-2 Securities resulted in a further adjustment to the conversion price (the “Subsequent Anti-Dilution Adjustment”) at which each share of the Issuer’s Series A-1 Stock, Series A-2 Stock and Series A-3 Stock is convertible into shares of Common Stock.  As a result of the Subsequent Anti-Dilution Adjustment, the effective conversion price of each share of Series A-1 Stock, Series A-2 Stock and Series A-3 Stock was reduced from $7.627 to $7.464.  Accordingly, following the issuance of

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the Series B-2 Securities, each share of Series A-1 Stock, Series A-2 Stock and Series A-3 Stock is convertible into 10.908 shares of Common Stock.

Following the Merger, the Short-Form Merger, the issuance of all Series A-1 Shares pursuant to the terms of the Series A-1 Stock Purchase Agreement, the issuance of all Series B Securities pursuant to the Series B Stock Purchase Agreement, the Series A-6 Dividend, the issuance of all Series B-2 Securities pursuant to the Series B-2 Stock Purchase Agreement and the Subsequent Anti-Dilution Adjustment, and assuming the conversion into Common Stock of all issued and outstanding shares of Preferred Stock of the Issuer, the Reporting Person owns 0.16% of the Issuer’s outstanding capital stock, with 63,964 shares of Common Stock issuable to the Reporting Person upon the conversion of 6,120 shares of Preferred Stock held by the Reporting Person.  An aggregate of 6,738 shares of Common Stock are also issuable to the Reporting Person upon the exercise of Warrants and New Warrants held by the Reporting Person.

Item 5.  Interest in Securities of the Issuer

Item 5 is hereby amended and restated in its entirety as follows:

(a)                                 Aggregate number of securities beneficially owned by the Reporting Person disclosed in Item 2: See Line 11 of the cover sheet.

Percent of Class:  See Line 13 of the cover sheet.  The percentage set forth on the cover sheet for the Reporting Person is calculated based upon 39,659,648 shares of outstanding Common Stock being deemed issued and outstanding, which consists of: (i) 879,370 shares of Common Stock that are issued and outstanding and (ii) an aggregate of 38,780,278 shares of Common Stock issuable upon conversion of all shares of Preferred Stock (after giving effect to the Subsequent Anti-Dilution Adjustment) that are issued and outstanding, as disclosed in the Issuer’s Annual Report on Form 10-K, filed with the SEC on February 26, 2014, in the Series B-2 Stock Purchase Agreement filed as an Exhibit to the Issuer’s Current Report on Form 8-K filed with the SEC on February 21, 2014, and as disclosed to the Reporting Person by the Issuer separately.

The Reporting Person disclaims beneficial ownership of the shares reported on the cover sheet except to the extent of his pecuniary interest therein, if any.

(b)                                 Regarding the number of shares as to which such person has:

(i)                                     sole power to vote or to direct the vote:

See Line 7 of cover sheets.

(ii)                                  shared power to vote or to direct the vote:

See Line 8 of cover sheets.

(iii)                               sole power to dispose or to direct the disposition:

See Line 9 of cover sheets.

(iv)                              shared power to dispose or to direct the disposition:

See Line 10 of cover sheets.

Schedule A attached to this Amendment No. 1 sets forth, as of the date hereof, the number of shares owned on an as-converted basis and the percentage of shares as calculated (a) based upon 39,659,648 shares of outstanding Common Stock being deemed issued and outstanding, which consists of: (i) 879,370

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shares of Common Stock that are issued and outstanding and (ii) an aggregate of 38,780,278 shares of Common Stock issuable upon conversion of all shares of Preferred Stock (after giving effect to the Subsequent Anti-Dilution Adjustment) that are issued and outstanding, as disclosed in the Issuer’s Annual Report on Form 10-K, filed with the SEC on February 26, 2014, in the Series B-2 Stock Purchase Agreement (as defined in this Schedule 13D) filed as an Exhibit to the Issuer’s Current Report on Form 8-K filed with the SEC on February 21, 2014, and as disclosed to the Reporting Person by the Issuer separately, and (b) in accordance with Rule 13d-3(d)(1) promulgated under the Exchange Act. All information with respect to the Separately Filing Group Members is based solely on the information contained in the Schedule 13Ds filed by the Separately Filing Group Members or on information provided separately to the Reporting Person by the Issuer.

(c)                                  Except as set forth in Item 3 above, the Reporting Person has not effected any transaction in the Common Stock during the last 60 days.

(d)                                 No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Shares beneficially owned by any of the Reporting Person.

(e)                                  Not Applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

Item 6 is hereby amended and restated in its entirety as follows:

The Reporting Person is a party to the Fourth Amended and Restated Stockholders’ Agreement, dated as of February 14, 2014, by and among the Issuer and the stockholders party thereto, which is attached as Exhibit 4.1 to the Issuer’s Current Report on Form 8-K filed with the Securities and Exchange Commission on February 21, 2014 and incorporated by reference herein.

Item 7.  Material to Be Filed as Exhibits

Item 7 of the Schedule 13D is amended and supplemented as follows:

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SIGNATURE

After reasonable inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Date:       March 5, 2014

[Signature Page to Amendment No. 1 to Schedule 13D]

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Schedule A

Certain Information Regarding the Separately Filing Group Members(1)

(1)All references to the number of shares outstanding are based upon 39,659,648 shares of outstanding Common Stock being deemed issued and outstanding, which consists of: (i) 879,370 shares of Common Stock that are issued and outstanding and (ii) an aggregate of 38,780,278 shares of Common Stock issuable upon conversion of all shares of Preferred Stock (after giving effect to the Subsequent Anti-Dilution Adjustment) that are issued and outstanding, as disclosed in the Issuer’s Annual Report on Form 10-K, filed with the SEC on February 26, 2014, in the Series B-2 Stock Purchase Agreement filed as an Exhibit to the Issuer’s Current Report on Form 8-K filed with the SEC on February 21, 2014, and as disclosed to the Reporting Person by the Issuer separately.  Because each stockholder of the Issuer is a party to certain agreements with the other stockholders of the Issuer, which agreements contain, among other things, certain voting agreements and limitations on the sale of their shares of Common Stock, each stockholder of the Issuer may be deemed to be a member of a “group,” within the meaning of Section 13(d)(3) of the Act (as defined in this Schedule 13D).  Shares listed as beneficially owned in this table exclude shares held by any of the Separately Filing Group Members, as to which the Reporting Person disclaims beneficial ownership.

(2) See the Schedule 13D (or an amendment thereto to the extent any material change in the facts set forth in any Schedule 13D previously filed by any Separately Filing Group Member has occurred) filed, or that the Reporting Person anticipates will be filed, separately by each Separately Filing Group Member, which includes, or will include, information regarding the filer’s jurisdiction of organization, principal business, and address of principal office.

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* Calculation of beneficial ownership percentage includes 5,124 shares of Common Stock held by H2 Enterprises, LLC, a company with which the Reporting Person is affiliated.

** Calculation of beneficial ownership percentage includes 23,048 options to purchase Common Stock anticipated to be exercisable within 60 days within 60 days of February 19, 2014 and 20,291 shares of Common Stock held by the Dr. John Potts, Jr and Susanne K. Potts Irrevocable Trust for Stephan K. Potts dated 6-15-05

*** Calculation of beneficial ownership percentage includes 680,317 options to purchase Common Stock anticipated to be exercisable within 60 days within 60 days of February 19, 2014.

**** Calculation of beneficial ownership percentage includes 203,432 options to purchase Common Stock anticipated to be exercisable within 60 days within 60 days of February 19, 2014.

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