Shares of HealthSpring posted their highest-ever closing price Thursday with a little help from the health insurance sector's biggest name. UnitedHealth raised its 2011 earnings guidance on the back of both better enrollment and lower medical costs, a potent combo that gave the entire industry a boost.

Not that HealthSpring shares (Ticker: HS) have needed help of late: Since the Franklin-based company announced its intent to buy Bravo Health last August, they've climbed 110 percent.

Investors Business Daily interviewed HealthSpring President Mike Mirt about his management team's decision making process. Read it here.

Analyst David Windley at Jefferies has lifted to $46 his price target for shares of Medicare insurer HealthSpring (Ticker: HS) ahead of the company's investor day tomorrow. There, Windley says, execs are likely to lower their EPS guidance to reflect their recent $301 million stock sale and — more importantly — talk positively about the Medicare environment these days. That should be good for the stock, which Windley has at 'buy.'

Thinking along the same lines is Josh Rankin at Barclays, who has hiked his HealthSpring target price to $48 from $44, making him the most optimistic on the stock, which has run up from the high teens since last August. Rankin has an 'overweight' rating on HealthSpring.

Shares of construction materials supplier Louisiana-Pacific (Ticker: LPX) are down more than 3 percent today after Credit Suisse analyst Chip Dillon lowered his rating on the company to 'neutral' from 'outperform.' Dillon is keeping his $13 price target for the stock, which until this morning had risen about 10 percent year to date.

It seems there's no stopping investors' stampede into HealthSpring these days: Less than a week after wrapping up a $300 million stock sale that temporarily pushed down its paper, the Franklin-based health insurer has charged up more than 10 percent and is changing above $40 for the first time ever. Volume is above the daily average for the seventh straight day.

HealthSpring (Ticker: HS) on Tuesday announced the closing of its public stock offering, having raised total net proceeds of $301 million by selling the inital 8,625,000 shares and the 1,125,000-share overallotment. The background is here.